Category : Physics

Question : What causes the earth to rotate around the sun, and what determines the speed of it's rotation around it's axis?

Answer : The sun's gravitational field has un trapped in perpetual "freefall" similar to satellites in orbit around the Earth (or our natural satellite, the moon). The Earth is in orbit around the sun and moves a horizontal distance (perpendicular to the sun) equal to how far it would have "fallen towards" the sun in the same time period had it been stationary. That is why we stay in orbit and do not either move closer and burn up, or move farther away and escape the solar system.

As for the Earth's spin I'm not sure why it began spinning but here are some resources that go into some detail on the spin itself (though they don't know why either - some venture some theories).

http://image.gsfc.nasa.gov/poetry/ask/q727.html

http://image.gsfc.nasa.gov/poetry/ask/arot.html

http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html

Paul Doherty
Rating : 3


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QAId : 345181
Asker : prakash_sankar
Subject : Physics
Private : No

Question : How do we see the different colors during sunrise and sunset?

Does air impurities and reflections play any part in the different colors of sunset and sunrise we see?

Answer : It's not "impurities" - it's air. Light in the uppper range of vision (blue and ultraviolet) interact with the air and are re-emitted like all frequencies as they pass through a medium but blue and ultraviolet interact more and are "scattered" more than the other frequencies, making our sky blue, and making the sun at it's zenith (overhead) appear more towards yellow (white light minue some blue). At sunset and dawn the sun's light is now travelling through the maximum of air possible and has even more blue removed than normal tinging the sun the familiar orange-red we all have seen. Particulate matter/pollution may intensify this effect but is not primarily responsible for it.

Paul Doherty
Rating : 5


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QAId : 345388
Asker : Anonymous
Subject : Physics
Private : No

Question : How does a nucleous of an atom split?

Answer : It's not just any old atom that can be "split" - and that's really a misnomer anyway as we don't do the splitting - the atom does so spontaneously under the right circumstances. Uranium is used for this purpose as it is a cumbersome atom being one of the most massive in terms of the number of nucleons present in it.


The nucleus, as you may or may not know, is composed of neutrons (negative charge) and protons (positive charge). When referring to a nucleus the protons and neutrons are collectively referred to as nucleons. A nucleon in isolation has a constant mass, or amount of material that makes it up. What is interesting is that this mass is *not* always a constant amount. What do I mean? Well for example, a hydrogen atom is the simplest element, consisting of a single proton in the nucleus and one electron in orbit. Let's say this proton has a mass of 'X'. In a hydrogen atom this is the maximum mass a proton can ever have. When more than one proton or neutron share a nucleus there is a strong nuclear force that bonds them together and that actually *reduces the mass of each element thus bonded.* If you were to measure the mass of a proton outside a nucleus you would find it at full mass. If you then measured it's mass inside a nucleus consisting of the proton and a neutron you would find some of the mass 'gone' in the form of the nuclear bonding force holding the two together. This is important to understand - I will now be using a term "mass-per-nucleon" which is an indication of the average retained mass (from it's normal full-mass state) of each element of the nucleus in different elements. It's a way to compare the loss of mass between differing elements (thus between differing atomic configurations). Once more than one nucleon is present in the nucleus the mass per nucleon starts to fall very quickly. The quickest change comes from hydrogen to helium since this is the very first introduction of a more mass-decreasing nucleons. As we move along the scale of atomic complexity (adding more protons and neutrons as we go) the mass-per-nucleon continues to drop as denser symmetrical nucleuses are formed. After one of the most stable and dense nucleuses, iron, however, something starts to happen. The atoms more complex (heavier) than iron start to reverse this trend, increasing in mass-per-nucleon. This is due to lack of symmetry in these denser atoms - some nucleons are not bound on as many sides as in the less-dense atoms thus increasing their mass (since the nuclear bonding force does not act as strongly when they are farther from neighboring nucleons - thus they lose less mass). When you get to an atom like uranium you have a highly unstable configuration which results in a high mass-per-nulceon. When uranium or plutonium absorbs a neutron they become unstable and electrical respulsion of the large number of protons overcomes the nuclear bonding force and the atom splits into fragments. The energy of a nuclear bomb or of a nuclear reactor comes from the fact that *the total mass-per-nucleon of the resulting fragments is less (since the fragments are more stable nucleuses and thus have more symmetrical layouts) than the mass-per-nucleon of the same number of protons and neutrons before the atom split* - this difference is the energy given off in kinetic (the fragments ejected during the splitting) and radioactive form.

Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com
Rating : 5


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QAId : 345459
Asker : djshewan47419
Subject : cold fusion
Private : No

Question : How close, or indeed how far are we from cracking cold fusion. Have there been any real advances? if so what are they?

Answer : It is unlikely we will find a way to perform cold fusion - the respulsive forces on two hydrogen atoms (being composed of one proton each) are too great to get them to meld without high temperatures (which require massive energy on our part). The sun is a standard fusion reactor, constantly fusing hydrogen atoms into helium atoms with high temperatures. If we can get a fusion scheme that can put outmore energy than it takes to run then we will have broken past the "break-even" point and our energy worries will be over. But I would expect it to happen in a "cold" manner - expect heat, and lots of it.

Paul Doherty

Answer : Fingers moving slower than my brain - that last sentence should read "wouldn't expect" not "would expect"
End :
Rating : 1


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QAId : 345522
Asker : w8hz
Subject : Sound of tree falling
Private : No

Question : This is an old rhetorical question but I think it is still interesting:

If a tree falls in a forest and there is no one there to hear it, does it's falling make a noise.

Thank you,

Bob ...

Answer : This is a great old question that simply revolves around whether one defines "sound" as:

1) A mechanical vibration through a conductive medium (air, water, etc).

OR

2) A psychological response to a medium vibration, requiring an organism equipped with vibratory-detection senses be present to experience it.

Paul Doherty
Rating : 3.1
End :
Rating : 3.1


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QAId : 375465
Asker : wlseese04946
Subject : heat conduction
Private : No

Question : What can you tell me about heat conduction? I am doing a lesson for sixth graders. Where can I find more information on it on the Internet?

Answer : Heat conduction is one of three methods for the exchange of heat, the other two being convection (involving circulating fluids) and radiation (electromagnetic energy (light)).

Convection occurs when materials that are good heat conductors touch. The thermal energy (high molecular movement average) is transferred by both impact (for all materials to some degree) and by the movement of free electrons in metals (which is why they conduct heat and electricity so well).

Here are some links to info you may like:

http://www.ronkurtus.com/physcien/heat.htm

http://physics.mtsu.edu/~plee/SCI_OUTREACH/heat1u.txt

http://www.jhu.edu/virtlab/heat/cond_des.htm

http://www.madsci.org/posts/archives/feb98/885153825.Ph.r.html

Paul Doherty
Rating : 3
Rating : 3


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QAId : 385040
Asker : Anonymous
Subject : speed light
Private : No

Question : How many times greater is the speed of red light(wavelenght=700nm) than the speed of blue light(wavelength=400nm)in a vacuum?

Answer : The speeds are the same - all electromagnetic radiation travels the same speed. If it didn't paintings would look horrible :-)

The wavelength is different for red and blue light as you indicated (blue being a shorted wavelength) but the piece missing from your question is that red and blue *also* have differing frequencies of oscillation. The blue light oscillates *faster* than red light does with the end result being that the same *distance* is covered by both (since the distance is the product of wavelength times frequency). Here is an illustration of the concept:

RED_LONG_WAVELENGTH X small_frequency

blue_short_wavelength X HIGH_FREQUENCY


Paul Doherty
Rating : 4.9
Rating : 4.9
Rating : 4.9


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QAId : 386688
Asker : er1n2006
Subject : nuclear fusion
Private : Yes

Question : I am in 6th grade. I am researching nuclear fusion and want to know when it will be available as a viable energy source.

Thank you for your help

Answer : Fusion reactions are when nuclei are slammed together to form a new, more dense nucleus. The trouble with this procedure is that the contents of each nucleus is at least one proton which has a positive electrical charge. Like charges repel each other so the two nucleuses are like the same sides of two magnets, pushing away from each other and the force gets much stronger as they get closer together. The normal method to get around this repulsive force is to generate lots of heat. Heat is nothing more than motion (kinetic energy) and if the nucleuses are made to move fast enough they can overcome their repulsion and be pushed against one another and form a new nucleus, giving off energy in the process. So our problem is three-fold: 1) generate enough heat to cause this to happen - we already can generate the heat to cause this 2) keep the heat/reaction going - this we cannot do and 3) get more energy out of the reaction than we had to put into it to start the fusion process - this also we cannot do.

If we can find a way to make the reactions happen without requiring lots of heat (the current situation) then we may see fusion reactors in our lifetime. With heat only it may take longer...


Here is a web page you might like about fusion:

http://stuweb.ee.mtu.edu/~kklafran/EE280.html

Paul Doherty
Rating : 3


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QAId : 391211
Asker : Anonymous
Subject : sound
Private : No

Question : The intensity of a 67 dB sound doubles and then increases by a factor of 10. What is the corresponding change in dB?

Answer : Well doubling the loudness brings thr 67db sound to 70db. And then increasing it by a factor of 10 adds 10db to a total of 80db.

Paul Doherty
Rating : 5


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QAId : 412933
Asker : grail
Subject : theoretical question
Private : No

Question : Don't think that this is just a goof off question, if water going down a drain goes counter clockwise in the northern hemisphere and the opposite in the southern, then what if you could, for the sake of argument, put half the drain in the northern hemisphere and the other half in the southern, what direction would it flow? I'm not crazy, I've always wondered this since I was a child.

Answer : The question isn't all that silly but is quite difficult (and useless) to answer. The reason it's kind of useless is the drain circling thing only occurs with *perfectly* still water with no disturbances whatsoever. Any disturbance is enough to easily overwhelm this (IIRC) "coriolis effect" and make the water drain in the opposite direction.

Force to answer the question when the water holder is arranged half norther, half southern I'd have to say that this is analogous to standing a coin on end and guessing which way it will fall. the forces are supposedly *balanced* but in fact are not, and the side on which the balance of torque falls, so falls the coin.

Paul Doherty
Rating : 4
Rating : 4


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QAId : 513030
Asker : Anonymous
Subject : nuclear fusion
Private : No

Question : what are the mechanics of generating this energy?

what are the costs of this energy?

what are the environmental considerations?

what are the advantages and disadvantages of this enegy?

what are the practical applications?

what is some other useful and unique information that you think is important?

Answer : To understand where we get the energy from, read this answer I gave on fission as the concept of where the energy comes from is identical in both fission and fusion. The only difference is that with fusion you bond two light nuclei into a third, denser one, and in fission you "split" a large nucleus into smaller elements.

http://www.askme.com/ViewAnswer.asp?vid=345388

Environmental considerations are better with fusion than with fission. The by-product of fission is radioactive materials - the by-product of one type of fusion (hydrogen atoms), however, is helium.

Some of the advantages are obvious - less pollution and almost infinite energy since, unlike uranium, hydrogen is one of the most plentiful elements in the universe.

Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 542147
Asker : lindo13149526
Subject : bounce
Private : No

Question : What is the relationship between the bounce of a basket ball and its air pressure?

Answer : I would think there would be a linear relationship (up to the point that the rubber's elasiticy is reached) from low to high pressure and low to high (potential) bounces.

With too little air inside the ball you get almost none of the rubber's elasticity as the ball weighs nearly the same with this low pressure and there is so much "mush" to the impact (time over which the force acts is LONG) that there is little chance of bounce. Once the pressure comes up to where the ball is taut both the rubber's properties *and* the air pressure inside combine to result in a bounce. Increase the air pressure more and the bounce is more pronounced until you reach the limit of elasticity (or you blow the ball apart with air pressure :-).

Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 567992
Asker : neon_genesis_evangeo
Subject : Bouncing of Tennis Balls
Private : No

Question : I was wondering why cooler tennis balls don't rebound as well as warmer tennis balls. Is it because of the atoms' lattice? Why? Thanks for taking time answering these questions. Keep answering those questions - we appreciate it. =)

Answer : I would imagine that it is simpler than that - it's more likely the reduced air pressure associated with the less-active (cooler) air inside the tennis ball not contributing as much to the rebound. Certainly if made cool enough the rubber's elastic properties can be reduced.

Thanks for the kind words!
Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 617741
Asker : cookiefighter13
Subject : cathode ray tube
Private : No

Question : In the television or computer, the cathode ray tube is the object that produces the light and images on the screen. The colors emitted are red, blue, and green. Why aren't they primary colors(red, blue, yellow) instead?
please send your answer to
cookiefighter13@yahoo.com

Answer : I think maybe you're confusing paints with light. The primary colors of light *are* red, green and blue. The difference between the primary colors between paints (or inks) and light comes from the way the color is perceived.

Light is additive - when more frequencies get added they "accumulate" for lack of a better word, culminating in the familiar white light which is all visible frequencies.

Paint is subtractive (in fact all objects we see are subtractive in the nature of how we perceive them). A red shirt is red because it absorbs all frequencies of light *but* red, as opposed to a neon sign (not the generic term, but actual neon - which glows red) which glows red because red is the *only frequecy being produced*. If you add in all the colors of paint to a canvas what do you get? You get black since you are no absorbing all the colors present in white light, leaving nothing left. This is also why black pavement gets hotter than a tan or white sidewalk - the black pavement absorbs the majority of the light striking it, while the lighter-colored materials reflect (in a fashion) the majority that strike them.

Paul Doherty
Rating : 5


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QAId : 623836
Asker : Brendar
Subject : atmospheric pressure
Private : No

Question : Are atmospheric and absolute pressures the same type of pressure?

Answer : Atmospheric pressure is pressure derived froim the weight of air molecules surrounding and above us. The only references I found to absolute pressure are related to scuba diving. Absolute pressure in this context is the combination of both atmospheric pressure *and* the water pressure (which being a fluid also increases as the amount above you increases).

Paul Doherty
Rating : 3


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QAId : 640964
Asker : i_got_email
Subject : neutrino
Private : No

Question : what exactly is neutrino? One property of its properties is that it interacts weakly with matter and is very difficult to detect. How does neutrino's weak interaction with matter affect the detection of its existence?

Answer : I am not really up on neutrinos so I will suggest a few web sites I found:

http://whyfiles.news.wisc.edu/004antarctic/
http://budoe.bu.edu/~superk/times.html
http://cupp.oulu.fi/neutrino/

Paul Doherty

Rating : 2


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QAId : 642636
Asker : saville@...
Subject : formula.
Private : No

Question : 91.4-((91.4-t)*(.478+(301*sqrt(v))-.02*v)) represents a formula that I believe is the velocity of an object falls. ie a skydiver.But I am not sure. Thank you for any help with this.
Gavin

Answer : I don't answer math-based physics questions but on this one it appears you have made it too complex.

IIRC velocity of fall (neglecting terminal velocity and air resistance in general) is:

gt


Distance fallen is:

1/2gt^2

And if you have some way to calculate the surface area of a skydiver you can figure out at which velocity terminal velocity kicks in and acceleration stops.

Paul Doherty


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QAId : 673705
Asker : Anonymous
Subject : science careers
Private : No

Question : I am wondering how a computer service technition relate to the field of science.

Answer : Well when you get down to brass tacks "science" is nothing more than a rigorous adherence to observation and past experience. So in that sense a computer technician employs scientific techniques all the time. For instance, when troubleshooting a problem with a system, a series of mini-experiments is conducted, to rule out which subcomponent or subsystem may be at fault. by knowing what functions apply to which areas, and by knowing how to test for functionality in each area you can isolate the faulty portion of the whole.

Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 675613
Asker : Anonymous
Subject : freefall
Private : No

Question : I have to do a research paper, on freefall, to graduate. Can you give me some imformation?

Answer : Freefall is pretty straightforward - it's just what happens to an object when it's freely subjected to a gravitational field. What happens is the full force of the gravitational field goes to accelerating the object towards the body providing said gravitational field. In the absence of an atmosphere this acceleration would continue (and get more intense as the proximity between the bodies closes) until the object smacks the surface. On our planet, however, air resistance is a factor with any fall lasting more than 10 seconds or so. Once the object has fallen this long air resistance builds up until it equals the weight (at that altitude) of the object - at which point no further acceleration takes place. This state of equilibrium is called "terminal velocity" and is the fastest the object can fall unaided (like unless you strap a rocket on it and face the rocket down :-)

Paul Doherty
Rating : 5


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QAId : 680132
Asker : scapp
Subject : Airplanes....
Private : No

Question : When you're on a plane with a drink, and the plane banks to make a turn, the liquid level in the cup barely moves even thought you're almost sideways. I know it has something to do with the pressurized cabin, but what is the point where the liquid will actually spill out if the cup? Or will it never spill?

Answer : The effect you're describing isn't due to the pressure in the cabin. It's due to the fact that even during a turn you have a huge momentum in the forward direction. Think about the plane like it's a large roller-coaster. When it heads into a corner it doesn't stay level with the ground - it banks around a corner at an angle to the ground so part of the forward momentum is experienced as "additional" gravity, like G-forces in a fighter plane. You would have to have a severe bank to get your drink to spill due to this additional force. A good way to understand it is to picture the difference between your drink sitting on the tray table with the plane at rest on the ground and using a crane to tilt the angle of the plane (it would spill when it would anywhere else on the ground - the liquid acting as a natural "level") and the dynamic situation that occurs when the plane is at the same angle of tilt but in forward motion and in a banked *turn*, not just tilted.

Another way to think of it is that a plane in a banked turn is becoming very similar (depending on the angle of the bank) to a rock tied to a string that is being swung around in a circle. The force that holds the rock in the circular path is communicated by the string (and provided by your arm). The force felt by the rock is that of the fake force, centrifugal force, which is nothing more than the tendency of the rock's momentum to carry it in a straight line.

In answer to your spilling question - yes the cup will spill, but at an increased angle compared to the same cup at rest on the ground.

Paul Doherty
Rating : 5
End :


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QAId : 691306
Asker : atorres947955
Subject : refraction and reflection
Private : No

Question : What is refraction? What is reflection? What is the difference between them?

Answer : A reflection is when a lightwave strikes a surface and in deflected back away from the surface. The most common example is a mirror. If you aim a light source at a mirror 20 degrees off-center to the left the light will be reflected at 20 degree angle to the right of center.

A refraction is the change in path associated with light *passing through* a transparent medium of some kind. This is caused by the slower speed of travel for light that passes through denser mediums like water or glass. While the instantaneous speed of light is a constant there is an absorbtion/re-emission process as light passes through that makes the end result of light taking longer to pass through (approx 75% the speed in a vacuum for light travel through water; 99% for light through air). A good example of refraction is looking into a swimming pool or bathtub and seeing the person's extremities being distorted or in the wrong position. The light is actually taking the shortest-time path through the medium which seems kind of odd, but it does. What this means, since light travels slower through denser mediums, and the fact that our brains perceive light as traveling only in a straight line, is that we see objects immerse in water at a higher height than they really are. Imagine a fish floating in the water at a short distance away and you are looking into the water at the fish, gauging his depth in the water. The light leaving the fish that strikes your eye takes the least-time path to your eye as I mentioned. What this means in practice is that the light wave is bent slightly towards the perpendicular (meaning it bends towards vertical) before striking the air at the water/air boundary. It's helpful to think of a lightwave as a small flat plane perpendicular to the direction of light travel - an easy way to picture this is to imagine a lawnmower at the forefront of the lightwave, that is being pushed froward by them lightwave. When the lightwave begins to enter the air it speeds up but because it's traveling at an angle the side of the lawnmower that enters the air first (the side closest to the vertical line) speeds up first, bending the direction of travel for the whole lightwave. This results in the shortest amount of *time* (not necessarily distance) of travel for the lightwave, but results in your seeing the source of the fish's light as coming from a direct line-of-sight location from after that last bend when the light emerged from the water. The spot you see the fish is actually higher than where the fish is located.

Paul Doherty



Rating : 5
Rating : 5
Rating : 5


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QAId : 693708
Asker : thebigcor
Subject : hi
Private : Yes

Question : okay here goes i lost a wallet weeks ago either i dropped it outside my car in front of my place ..or i lost it in my house, or someone took it out of my car.. what do you see about this.. also i want to know what you see as far as me selling this jeep wagoneer i have that i had to repay a buyer back and than i fixed it with all my money will i sell it asap. i hop.. hey hows my love life look i hope something happens soon.. corey 12/10/65

Answer : I think you've confused the word "physics" with "psychics" - I feel no vibrations in your general direction, perhaps a 1-900 number can help? :-)

Paul Doherty
Rating : 5
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QAId : 721665
Asker : lazb0y
Subject : Nuclear Fusion
Private : No

Question : Hiya I have a large essay to do on Nuclear Fusion and I am doing research at the moment.I was wondering if you could offer ANY information or literature on the subject.
Thanx

Answer : Sure thing - just open the URL below, which is answer I gave on the same topic (it in turn references another one I answered on fission and fusion).

http://www.askme.com/ViewAnswer.asp?vid=513030

Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 735870
Asker : Anonymous
Subject : electricity
Private : No

Question : Explain why I am more likely to get a shock by walking across a carpet in Jan. than in Jun (at least in mid-west area) Where might the opposite be true?

Answer : Your liklihood of being shocked across a carpet has to do with the amount of moisture in the air. The less humid it is (the less moisture in the air there is) the more likely you are to carry a voltage differential along with you. The more moisture in the air (higher humidity) the faster the charge you produce will "leak off" into the air, making it less likely for you to receive a shock. It's usually less humid (and there is a lower cap on relative humidity) in January when it's cold than in June when it's relatively warm. Relative humidity is the measure of what percent of the air contains water vapor as compared to the maximum amount that *could* be in the air *at that temperature*.

So somewhere where the humidity is almost always high is a place you would be less likely to get shocks.

Paul Doherty
Rating : 4.9
Rating : 4.9


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QAId : 745512
Asker : emeraldinmay@...
Subject : reflection
Private : No

Question : what is reflection? what is a good experiment to demonstrate reflection? (i am 11). thank you.

Answer : A mirror is the most common, and easiest to see, example of reflection. Ask your Mom for a pocket mirror or hand mirror and hold it up to your face. The image you see is the result of the reflection of light rays leaving your face and bouncing off the mirror into your eyes. A surface becomes a mirror if the irregularities (present in all materials at some level) are small enough to be "invisible" to the wavelength of light that strikes it. In other words a mirror is just a mirror because it's smooth enough to not randomly scatter the light that strikes it, but rather uniformly deflects it.

Here's another question I answered on reflection and refraction that you might want to read with your parents:

http://www.askme.com/ViewAnswer.asp?vid=691306

Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 761103
Asker : acyran84929
Subject : static
Private : No

Question : How does the use of fabric softener in the dryer prevent static cling?

Answer : I found just the site for you:

http://www.pg.com/schldays/fabric/24101.htm

Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 803664
Asker : Tatencio09457
Subject : Quantum physics
Private : Yes

Question : Hello,
I have always avoided math and science. However, quantum physics intrigues me. Will you tell me the basics of it, and do you think time travel is possible, or "warp" travel? I'm not a dope - my forte' is art and music! Thank you for your time.

Answer : You asked a mouthful... one of the main precepts of quantum mechanics that differs from traditional physics is the concept of uncertainty. Where traditional physics makes an underlying assumption that all events can eventually be dissected into their constituent parts, quantum physics has no such illusions. The main idea that illustrates this dichotomy is that of Heinsenberg's Uncertainty Principle. This principle is perfect for this discussion because it shows that, even in theory, it is not possible to know all the factors one would need to know to predict sub-atomic collisions. In macroscopic physics, for example, if you were going to throw a tennis ball at a wall and could gather enough information in advance about the pull of gravity, the arc and initial velocity of the tennis ball, the elasticity of the ball and the wall as the ball strikes the wall, the friction of the ball as it strikes the ground and rolls, and so on, you can predict with great certainty where the ball will end up and the course it wall take on it's journey. We would like to be able to apply those same rules of momentum and trajectory in predicting subatomic collisions. Unfortunately the same can not be said of the predictive ability of physics at this level. The reasons have to do with the nature of viewing an event and with the sizes of the objects involved. When we view an event in the macroscopic world we make almost no impact on the objects being viewed, such that we tend to ignore the fact that our mere presence does have an effect on the outcome of the event being measured. In the subatomic realm our observational impact cannot be ignored and has a serious impact on the results of the very thing we are measuring.

An example of a thing we would like to be able to apply our predictions to, and be able to measure, would be the collision of two or more subatomic particles like electrons. Why can't we just get the same information about it that we got about the tennis ball and go from there? The two main pieces of information we need about the electron to predict what will happen to it when it collides are it's velocity and direction of travel. We knew both of these to a good precision about the tennis ball before it's collision which is what enabled us to be highly accurate in our prediction. The problem comes in when you try to determine both of these items for an object that is as small as an electron. The first problem is even seeing an electron, given the miniscule diameter of one. What we have to do to see an object as small as an electron is to move upwards in the electromagnetic spectrum. Whereas we could use visible light to view the tennis ball before, during, and after the collision we cannot use those wavelengths to view an electron since the wavelengths of visible light are far too large to reveal an object so small as an electron. The visible light frequencies would be like a semi truck that strikes a butterfly in flight - unaffected and unaware that anything has taken place. The visible light frequencies are too "coarse" to reveal such a tiny diameter object. So what do we do then? We start shortening the wavelength in a search for one short enough to reveal our electron. The problem is that as you move higher into the electromagnetic spectrum each successively shorter wavelength carries with it a higher energy per photon (a photon is a "packet of light" - the smallest unit of light emitted at one time from a electromagnetic source). For example you don;t wear sunscreen inside your home do you? That's because the visible light frequencies produced by the incandescent or flourescent bulbs in your home do not have enough energey per-photon (they are relatively long-wavelength radiation with a short frequency) to harm your skin. But outside where the sun's rays leak through the atmosphere a lot of ultraviolet gets in (which is a shorter wavelength than the shortest visible wavelengths of blue light) and it contains enough energy per photon to do damage to your skin. So the same way the shorter-wavelength, higher-energy ultraviolet light can damage your skin the higher we go in search of a frequency to reveal the electron the more energy per photon we will be imparting to the objects we attempt to view. By the time we dial up to a wavelength short enough to "see" an electron so we can pinpoint one of our items of interest, it's exact location, we are in the neighborhood of gamma radiation and are imparting a huge amount of energy per photon. When we use this frequency to find our electron we can know it's exact position which is one of the things we need to know to predict it's impending collision. The problem comes from the massive energy per photon and the fact that electrons have very little mass. We now have pinpointed the electrons position to a good level of accuracy but now, in using such a high-powered radiation to illuminate it's position, we impart so much energy to it (and due to it's small mass) we send it flying off in an unpredictable direction so we now know nothing about it's velocity. That's bad so now we dial down our wavelength to one that can show us the velocity of an electron but doesn't impart enough energy to send it careening. Know we know what direction it's heading with good precision but we're back to our original problem - we don't have fine enough resolution to pinpoint it's location!

So what this boils down to is that we can know *either* the position or the velocity of the electron at any given time but not both at the same time, which means we cannot apply the same types of predictions to it, even in theory, as we did to the tennis ball.

Paul Doherty

Answer : I forgot to answer the warp travel question...

I don't have any information about time or warp travel, other than to have heard of supposed faster than light travel particles I believe are called "tachyons".

Paul Doherty

Answer : I typo'd on the name of the founder of the Uncertainty Principle - it's Heisenberg.
Rating : 5


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QAId : 812313
Asker : scdoom13
Subject : air and ice
Private : No

Question : I am a seventh grade student and I would like to know why when air gets cold it contracts but when water ets cold it expands. Such as when a balloon is cold it shrinks but if you fill i water bootle up to the top and freeze it it will expand and maybe pop the bottle. Why is that?

Answer : A very astute observation. Most people don;t notice this strange inconsistent behavior of water. Considering that for almost all other materials the order of least to most dense is gas, liquid, soild, it stands to reason that water is odd for the fact that the solid form (ice) floats on top of the liquid form, and indeed forms on the top of the water first!

Water behaves in this strange way due a unique crystalline structure that water undergoes when freezing (becoming a solid). The open hexagonal structure actually takes up *more* space in this form than the same quantity of water in liquid stage. The end result is that the ice is of a lower density (less material per unit of volume) and thus is "lighter" than the same volume of water and floats. As to why it freezes on the top of the water as water is chilled from warmer temperatures it does indeed become less energetic and more dense. This continues down to about 4 degrees Celsius, just above freezing. At this point ice is at it's maximum density and this 4-degree water sinks to the bottom of whatever container is present (lake, sea, ice cube tray, etc) and warmer water moves in to take it's place. Cooler than 4 degrees C is where the crystalline structure begins to form which makes the water less dense as it moves towards freezing. Only after ALL the water in the container has been coooled to 4 degrees Celsius can further cooling take place. The most commong example of this is a lake whose top freezes over for ice skating in the winter. The whole body of water was at 4 degrees C before freezing from the top down (where the colder air cooled it). This also explains why the oceans don't usually freeze at all even during the coldest winters. They don't stay cold enough long enough for the entire depth to reach 4 degrees Celsius. And this answers the age-old question of:

What temperature was it at the bottom of the ocean on December 2nd, 1961 at 2:24 AM?

Answer - 4 degrees Celsius... because it always is.

Paul Doherty
Rating : 5


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QAId : 817264
Asker : irod7895954
Subject : special theory of relativity
Private : No

Question : in what decade did einstien come up with this theory?

Answer : It was in the firstd decade of the twentieth century (1905):

http://sci.hkbu.edu.hk/math/einstein.html

Paul Doherty

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 832634
Asker : bec72
Subject : clouds
Private : Yes

Question : Hi Paul, this is something I often wonder about and occasionally ask some one in passing (who generally then tell me to get a hobby!!). Maybe you can help.

A cloud is sort of ball of gas right? Does it have the same weight as it's elements combined. I mean, if 1 litre of water weighs 1 kg, how the hells does a cloud float through the sky??

I'm sure it's a simple misunderstanding on my part... hoping you can do an "idiots version' for me..

Rebecca.

Answer : I guess the area of confusion is that, while a cloud can produce water in the form of rain or snow, the state of the matter inside the cloud before rain is in the form of particulate matter (fancy way of saying "really small") - water vapor and particulate matter. When these elements combine that is condensation, and is what forms water droplets which then have enough mass to fall as rain.

I hope that helped a little... and BTW - get a hobby! ;-)

Paul Doherty
Rating : 5


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QAId : 892470
Asker : billly36
Subject : Relativity
Private : No

Question : I know the theory of relativity, but I do not understand why time would slow down at very high speeds. I have been pondering this for quite some time..... could you please help me out?
Thanks!

Answer : Physics doesn't dictate the way the universe is - it merely attempts to describe the way the world is in a way that is predictable and useful.

The reason time slows down near the speed of light is apparently so that the speed of light remains a constant. That is, even people travelling near the speed of light, would measure light in their vicinity to be travelling at the same rate as when they were standing "still" (no such thing really - all the universe is in constant motion - one of the cornerstones of relativity).

Paul Doherty
End :
Rating : 3


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QAId : 901431
Asker : yciros54555
Subject : Ocean Tide
Private : No

Question : The gravitational force of the Moon attracts the Earth, so there is ocean tide. But if the ocean tide is due to the attraction of the moon, then the high tide should always facing the moon, but in actual case, there are two tides, one on the side of the Earth facing the moon , the other on the opposite side of the Earth ,away from the Moon. Why? I have this question when I was 10 when my shool teacher told me there are always two high tides. Now I am 43, I still cannot find an easy answer for this question. Of course I mean an easy answer is an answer that does not use complicated mathematical theory. Can you find solve the question for me? Thank you .

Answer : Sure thing - first another question that should come to mind when thinking about the gravitational influence of the moon causing tides is this: the sun's pull at even it's great distance is still 180 times stronger than the moons, yet it's tides are much smaller than the moons. The reason for this (which also leads to how the moon's tidal forces work) is that the strength of gravity falls off as the inverse-square of the distance between two bodies. That is a fancy way of saying that if you have two bodies X distance apart there is a force of gravity (call it "Y"). If you double the distance between the bodies there is now only 1/4 the gravitational force. If you make the distance three times as far apart as the original the power is now 1/9th as strong. And so on. So with the distance over which the sun's gravitational influcence acts it's force has been greatly reduced, and the *difference between it's force on either side of the Earth is negligible, compared to the distance from the sun*. The moon's gravitational power, with it being so much closer to the Earth, is still fairly strong when it reaches the near side of the Earth, and this power falls off fairly significantly (again by the inverse-square law) on the opposite side of the Earth, making for a large disparity in pulling force on either side of the Earth. Think of the Earth as a ball of jello - if you pull on all parts of the jello at once the general shape is maintained. If, however, you pull more on one side than the other the shape become elongated. The side closest to the Earth gets pulled the most, with the center of the Earth being pulled less, and the far side pulled the least (allowing it to bulge ("stay where it is")). These bulges stay in place and as the Earth rotates underneath these influences we pass into them and see a corresponding rise in water levels as we pass through either bulge. The other component here is that you cannot think of the Earth as stationary relative to the moon. The Earth and moon both rotate about the "Earth-moon" center of mass. This movement and resulting centripetal acceleration (on the sides facing both towards and away from the moon) help account for more of the elongated shape of the Earth. The moon too is elongated from it's proximity to the Earth and thus has "tidal bulges" too - just no water to show it as much.

Paul Doherty
Rating : 4
Rating : 4


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QAId : 907080
Asker : TobiasJ13
Subject : Bicycle question
Private : No

Question : Consider the following situation:
Two people are riding identical bicycles down a decline. One person, though, is considerably heavier than the other. Will they both reach the bottom at the same time, if they both started from rest at the same time? Also, after reaching a flat at the end of the decline, will either go farther if no further energy is inputted?
I've been arguing with my friend who claims I have an advantage going down hills (though certainly not up) because i'm heavier. I claim we'd both be going the same speed because of the conservation of energy, but she still insists i'm wrong. Any light you could shed on this would be a great help. Thanks.

Answer : If we assume frictionless parts on the bike, identical bicycles, and that your top velocity doesn't approach that where wind resistance becomes a factor I would agree with you - both of you will travel down the ramp at the same speed (due to same acceleration from gravity) *but* I believe that the heavier person will travel a bit farther after level due to his increased momentum (being mass x velocity). It will take a bit longer for friction to slow his greater mass.

Paul Doherty
http://members.home.net/iqueue

FUQuestion : Thanks for that answer, but there is one more related question I have. Since I am heavier, raising the center of gravity of the bike (albeit slightly), and we generally consider gravity as acting on the system's center of mass, wouldn't the parallel component of the gravity correspond to an increased torque on the wheel (due to a larger radius from the axle) and cause me to go faster?
Rating : 4

Answer : I don't believe so, since your entire weight acts at only two points - where each tire meets the plane. The only effect your higher center of gravity would cause is that at steeper inclines you would produce a torque (and fall forward) sooner than the lower center-of-gravity rider would.

Paul Doherty
http://members.home.net/iqueue


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QAId : 955498
Asker : r_pem32979
Subject : resistance
Private : No

Question : can u plz help explain how resistance in a wire is related to length....
thankz
reena (:

Answer : Well resistance comes from the fact that work must be done to move electricity through a wire. The longer the wire the more resistance must be overcome - think of it as inertia - the electrons in the wire are at "rest" and you are attempting to coerce them into motion.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue

FUQuestion : can u plz send me a more deatailed explaination plz.....could u try and give me the resources u get this info from is well plz
thankz
reena

Answer : As far as more detailed explanations, examine the web resources below - the following is a quote from the first:

"The collision of electrons with atoms gives rise to resistance - the material resists the flow of the electrons and the amount of resistance will depend upon the nature of the material. Some materials such as metals have low resistance whilst others, like rubber, have high resistance."

http://io.newi.ac.uk/buckleyc/electric.htm

http://www.sci-ctr.edu.sg/ScienceNet/cat_physical/cat_gen01470.html

http://www.exploratorium.edu/snacks/short_circuit.html

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue

Answer : This is the other one to rate (in case you couldn't find it)

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 4.9
Rating : 4.9


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QAId : 977962
Asker : libertylabs
Subject : matter and energy
Private : No

Question : As I understand it, all of the matter that has ever been in the universe is still here. Is all of the energy that has ever been here, still here also?

Answer : I would say yes - the old axiom is that matter and energy are never destroyed - they just change forms. What was once chemical energy becomes heat (fire) - what was once potential energy becomes light and heat (sun's fusion), etc... The universe is like a large terrarium(sp?) - self-contained.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue


Rating : 5


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QAId : 978321
Asker : Anonymous
Subject : physics help
Private : No

Question : I need some help on these true/false questions. Thank You.

1. In a flowing fluid, the pressure where the fluid is moving slower is higher than the pressure where the fluid is moving faster?__

2.The upward force exerted by a fluid on an object immersed in it is called the buoyant pressure?__

3. The buoyant force that keeps a ship afloat is an example of Pascal's principle?__

4. The brakes in a car work because of Pascal's principle?__

5. A hot pizza contains heat?__

6. You can increase the temperature of a gas by compressing it?__

7. Air at a temperature of 32 degree"F" has a relative humidity of 60%. If the temperature of the same air increases, the relative humidity increases?__

8. Current is the rate of flow of electric charge?__

9. Voltage can also be called potential?__

10. A potential difference is necessary for current flow?__

Answer : 1 True - this relates to Bernoulli's Principle - it's easier to understand this if you think of a fluid as having a set amount of enery - it can use this energy for one of two things - movement or pressure. the more of one you have, the less of the other you have left. This is how planes get life on their wings (wind passes faster over the top so there is more pressure below the wing), and how tornadoes do damage (house blow themselves apart since the static air inside the house has greater pressure than the high-speed winds outside).

2 True - bouyancy comes from the difference between the pressure on the top (less since it's not as deep) and the pressure on the bottom of a submerged object. If the object weighs less than the amount of water it displaces (volume) it will float (or hover).

3 False - Pascals's principle is that pressure is exerted in all directions in a fluid. Archimedes principle has to do with bouyant objects like a ship.

http://www.mohawk.net/~viking/physics/arch.html

4 True - the fluid in the brake lines experiences an increase in pressure due to it being transmitted from the brake pedal to the lines hydraulically. The fluid exerts the same pressure everywhere through the brake system.

5 False - nothing *contains* heat - heat is merely a measure of the thermal activity of a substance. An object itself can be hot, but not conatin heat.

6 True (I think) - making a gas take up less space than it previously contained will result in a higher temperature.

7 False - Relative humidity is a measure of how much water vapor the air *could* contain *at that temperature*. Hotter air can conatin more moisture than colder air so taking air at one temp 60% RH and increasing the temperature alone will decrease the relative humidity since the warmer air can now contain more moisture.

8 True

9 True

10 True

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 5


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QAId : 984922
Asker : rtorres
Subject : CUAC-CUAC echo
Private : Yes

Question : I know that the duck sounds (cuac-cuac) do not produce echo sounds, do they?

If it is true ¿Why?

Thanks a lot

Rubi Torres

Answer : No, it's not true - ducks quacks echo like any other sound. Absent destructive interference (which would require precisely chosen environments and source sounds) sound is sound and will reflect equally from an echoing surface. See the URL below for a more entertaining version of the same information by Cecil Adams, my hero:

http://www.straightdope.com/classics/a5_071.html

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 5


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QAId : 985485
Asker : r_pem32979
Subject : superconductivity
Private : No

Question : can u plz superconductivity to me.....include resistance.
thankz
reena (:

Answer : Superconductivity is the effect, whereby a material is cooled to near absolute zero, resistance in the wire drops to nothing. Some materials have been discovered (so called high temperatue superconductors) that can reach this state at warmer temperatures (they are still quite cold relatively-speaking). Japan has a MagLev train (Magnetic levitation) train that runs on magnetic fields and uses superconductors. Their newest superconducting tarin will reach 340 MPH! See the URLs below for more details on superconductivity:

http://library.thinkquest.org/20872/intro.html

http://230nsc1.phy-astr.gsu.edu/hbase/solids/scond.html#c1

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue

Answer : Please rate the answers you receive on AskMe.com - I would appreciate your rating these last two on resistance.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 5


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QAId : 988804
Asker : Anonymous
Subject : light speed
Private : No

Question : Does light always travel at the same speed?

(According to the most modern theories)

Is matter time? could time exist without time? Are matter and time bound up endlessly in themselves?

Do you believe that there is a world which exists independent of our minds?

Do the perceptible (sensible) qualities of an object exist outside of the mind?

Answer : Yes light *propagates* always at the same speed - that is the instantaneous speed of light is a constant. Light, however, can be made to travel slower like passing through our atmosphere or water.

Matter is time...? I would say if anything motion *of matter* is time. Our concept of time is heavily wrapped around the concept of motion of physical objects (planets, stars, electrons, etc).

The world we live in exists independed of our minds - our only contact with the world we're in now is the input from our senses from which our mind constructs a replica of reality. Watch the 10:00 news programs and you'll see that some people's reality-generating abilities differ from ours.

The perceptible qualities do exist as I can build a machine to confirm that what I perceive it also perceives.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 4.6
Rating : 4.6


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QAId : 1010487
Asker : dead_sou24499
Subject : speed from a skid??
Private : No

Question : How do you determine the speed that a vehicle was going from the skid marks it left behind when it stopped? and what does the coefficient of friction have to do with it???

Answer : Well I would expect you would need to know the vehicles weight (so you can calculate it's momentum to find it's starting speed) in addition to the coefficient of friction - the latter being related to the speed since it dictates at what rate the speed is bled off by the tires and road (higher the friction the faster the speed is reduced).

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 4


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QAId : 1012578
Asker : Anonymous
Subject : drive
Private : No

Question : hi can u tell me the diference between fat32 and fat16 for the file system. I have fat 32 and I rember being at fat16 but i never changed the system and no one else uses the pc but me???? Also i have this other porblem last week i had 1.9 gig of hard drive speace and this past friday it said I had 978mb left on my c drive which is the main drive. and on that same day i went to the movies and left my pc on and i checked the drive space and this message came up saying i was out of disk space???? and i never installed anything for the 2 hours i was gone?? i checked for virus and nothing came up then i defreamgented my drive. and I check for errors to. then the next day it was back to 978mb but it goes of and on it decreased the drive space with me installing nay programs or anything. Asl is there anyway to restore the pc ot fat16?? also might that be the problem thank you.

Answer : FAT32 is a newer MS file system that can handle larger disks while simultaneously using smaller clusters which waste less space than larger clusters.

Likely if you had a FAT16 and it's not FAT32 (how dod you know this?) someone ran the FAT32 converter on your PC. It's located in Start/Programs/Accessories/System Tools/Driver Converter (FAT32).

As far as running out of space one of a coupld of things can be happening:

1) You have lots of small files, which means your reported space available is not accurate as you near disk full - considering you had 978MB reporting free I doubt this is it unless the disk is large.

2) You have a misconfigured BIOS that is not properly translating the disk size for Windows. Windows in turn bases it's disk space estimate on this erroneous information. To fix this involves changing the settings in the BIOS to AUTO and LBA but may require a reformat. It's also possible your BIOS can not handle the full capacity of your disk in which case you need to go to the disk manufacturer's website and get their disk overlay software (for example "MaxBlast from Maxtor for their drives) which will do a one-time install to the disk to provide this ability.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue

Answer : Don't forget to rate the answers you receive on AskMe.com
Rating : 5


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QAId : 1012853
Asker : Anonymous
Subject : Physics help please
Private : Yes

Question : Hi I am currently in a physics 101 class and have a 90 questions - I have answered all but i am stumped on the following and could desparately use some assistance - your time is greatly appreciated.

1)When a bar magnet is broke in two down the middle, each piece is a)as magnetic as the original magnet b)actually stronger than the original magnet c)half as strong as the original magnet d)no longer magnetic. -- i know d is out.

2)When a magnet is thrust into a coil of wire, the coil tends to a)attract the magnet as it enters b)repel the magnet as it enters c)both of these d)neither of these.

3)A wire moving sidewise in a magnetic field has NO induced voltage if a)it is moving in the direction of the field b)it is moving opposite the direction of the field c)it is made of copper d)it is moving very fast e)two of these.

4)If a magnet is pushed into a coil, voltage is induced across the coil. If the same magnet is pushed into a coil with twice the number of loops a) one half as much voltage is induced b)the same voltage is induced c)twice as much voltage is induced d)four times as much voltage is induced e)none of these.

5)A variety of sunset colors is evidence for a variety of a)elements in the sun b)apparent atmospheric thickness c)atmospheric particles d)atmospheric temperatures e)primary colors.

thank you so much.

Answer : 1) C

2) B (it *resists* the intrusion of the magnet is a better way to say it - because if you stop progressing there will be no net force on the magnet.

3) Not sure of the visual here but I suspect it would be A & B

4) C

5) B

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 5


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QAId : 1043483
Asker : SimonB
Subject : Physics in music
Private : No

Question : I have just been asked a question by a student of mine which I don't know even if its true. Is a middle C on one instrument different to a middle C on another instrument and if so why?

Thanks in advance

Simon

Answer : A "middle C" refers to the frequency of the sound, so for all instruments playing on the same clef a middle C is the same. The reason they don't *sound* the same is that the instruments all differ in their timbre - that is, each instrument's materials and composition color it's sound to make it unique.

Paul Doherty
http://members.home.net/iqueue
Rating : 4


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QAId : 1055327
Asker : becca11
Subject : electromagnetic radiation
Private : No

Question : What is electromagnetic radiation?

Answer : It is energy, plain and simple. When an atom becomes excited, by physical or electrical means, it's electrons become elevated to levels above their normal orbits. These electrons then drop back to their normal unexcited state and in the process give off the energy they gained. Since the orbits are at definite levels apart from each other, and since the electrons cannot reside between these levels, the energy given off by an electron going through this de-excitation process is said to be quantized. Quantization in this usage means that the energy is given off in discrete steps of energy. This excitation and atomic quantization is where we get some of the things familiar to us. As you probably already know electromagnetic radiation (I'll call it ER from here on out) in the ranges that our eyes use is generally called "light". So light is produced by this same mechanism - electrons get excited up to a higher-than-normal orbit, and then de-excite, giving off the energy they had gained in the form of a photon (quantized "piece" of ER).

Here's a good example of the quantization of light. I'm sure you've seen the so-called neon signs in convenience stores and such? Those signs are an excellent example of the quantized nature of electron orbits. Those lamps contain a pure gas - in the case of the bright red ones it's neon. The particular combination of electron excitation/de-excitation steps available to the neon atoms is what gives neon it's characteristic red color. Argon is another gas used in these lights and has a blue color for the same reason. Each type of gas has it's own characteristic pattern of available electron orbit hops that give it unique color. Contrast these types of lights with an incandescent light like in your house or on your car. These use a metal filament which when heated glows and gives off light. the same process if happening as in the gas but we get (closer to) pure white light from this type of bulb. Why? It's because now, instead of the limited nmber of combinations of electron orbit hops we had with a gas (where atoms are relatively far apart), we have a solid material with atoms shoved close together. The result being that electrons who make a hop to higher energy orbit in one atom may very well de-excite into a nearby atom making the energy patterns closer to infinite which also makes the frequencies of emitted ER nearly infinite - white light. A flourescent bulb works like a neon light but produces white light. How is that? It uses mercury vapor inside the tube, which when a current is passed through excites and gives off the standard limited number of patterns a gas can produce. But this light isn't even visible - it's ultraviolet in frequency. the white light actually comes from the spray coating on the inside of the tube - this solid material absorbs, and becomes excited by, the UV light and in turn gives off it's own less-limited pattern of white-ish light.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue

Rating : 5
Rating : 5


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QAId : 1061949
Asker : AstroConstant
Subject : 3 Questions
Private : No

Question : 1. Why waves require a medium to travel?



2. Why the electrons move only in one direction not the other? What is the force responsible for that?



3. What is the fourth dimension?

Please answer all these questions adequately.

Thank You.

Answer : Waves (sound, motion) require a medium because a wave is nothing more than *a disturbance of a medium*. Without the medium there is nothing to "wave". Light waves of course do not require a medium but they are not waves in the same sense (they travel as a wave but interact as a particle, and are energy, not matter).

I'm not sure what this #2 question is asking. Under what situations are you saying electrons move in only one direction?

The fourth dimension is commonly understood to be - time.

Paul Doherty
http://members.home.net/iqueue

FUQuestion : I meant that in an atom why all its electrons move in only one directon all the time? Why don't they change their direction?

Sorry that I couldnot tell You what I exactly meant.

Answer : No problem...

I don't know anything about electrons moving in only one direction - in fact I don't believe that to be the case. Where did you get this fact? Electrons travel as waves in the electron orbits and can exist at any point inside their "electron cloud" at any moment, irregardless of their previously-measured position. The old model (Bohr's) planetary-style orbits were not completely descriptive of the motions of electrons, but as it turns out are explained by the fact that each orbit is a multiple of an electron-wavelength, which also handily shows why electrons only exist at orbit levels and not between.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 5


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QAId : 1063457
Asker : Anonymous
Subject : carbon dioxcide
Private : No

Question : What is the painless to do youself in, suidice

Answer : I hesitate to answer such a loaded question. I hope that you are not considering such a thing yourself. Please contact me at my email address bitbucket911@home.com and I can answer the question if all you are is curious, or we can talk if not.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue




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QAId : 1075481
Asker : Rellia
Subject : Hockey
Private : No

Question : How does physics relate to hockey?

Answer : Well, other than research methods, not a lot... ;-)

A couple of things come to mind immediately when thinking of hockey and physics:

regelation
inertia
momentum

I'll briefly discuss each...

Regelation takes place at the boundary between the ice skates and the ice. Regelation is the process of ice melting under pressure and then immediately refreezing when the pressure is removed. Here's a little thought experiment: take a large block of ice and drape a metal wire across it with two large weights, one on each end of the string. This string will melt the ice immediately beneath it due to the pressure from the weights. What will happen is the wire will move down slightly into the ice and the ice (now water) above it's position will refreeze. this process will continue, with the ice immediately below melting, only to freeze after the wire passes, until the wire has passed all the way through th block of ice. And what are you left with? A block of ice very similar to the one you started with. That process is regelation. Ice skates cause it too, since they support your body's weight. On such a small amount of surface area the pressures produced cause regelation to take place. So as the skater moves across the ice the ice is constantly melting the ice with the pressure of his skates, with the ice melting behind him. So in actuality you aren't skating on ice at all - but rather a thin layer of water on top of ice! This is the reason those ice-surfacing machines are used as frequently as they are - the ice is deformed by the constant melting/re-freezing cycle.

Inertia are similar concepts - inertia is the tendency of an object at rest to stay at rest, and an object in motion to stay in motion. Inertia can be summarized as "objects tend to resist changes in motion" whether it be accelerating or retarding forces. In hockey inertia is evidenced by skaters who start in a line of travel and then, with no further effort, glide across the ice for large distances. This is due to the low level of friction (one of the forces than can impede on inertia's natural inclination to continue in the direction of travel) of the regelated ice.

Momentum is like inertia in motion. It is a measurement of an objects' mass and it's velocity, which give an indication of how hard it is to stop the object. Witness a heavy hockey player who hits a wall or another player. The wall or the player hit will show the result of dispersing the hockey players' momentum (one of them may not like it much, either :-). Since momentum is the product of mass and velocity the same amount of momentum can be generated by a less-heavy hockey player who travels faster. This is why bullets can damage or kill even though their mass is small. Their velocity is extremely high and the result is a high momentum.

I guess that was less brief than I intended (that always happens) - I hope that was what you were after...

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 5


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QAId : 1085376
Asker : david_hodges
Subject : weight of water
Private : No

Question : Could you please help settle a bet; How much does an imperial gallon of water weigh and could you please show your proof.

Answer : My understanding is that a gallon of water weighs 8 pounds at sea level. Proof? Weigh one yourself and see...

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 1
End :
Rating : 1


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QAId : 1102946
Asker : sporty21985
Subject : BUMPER CARS
Private : Yes

Question : STATE ONE OF NEWTONS LAWS AND TELL HOW IT APPLIES TO THE BUMPER CARS

Answer : That would be Newton's third law of motion usually summarized as:

For every action there is an equal opposite reaction. This emphasizes that actions take place among *pairs* of objects. This law applies to bumper cars since each car imparts it's momentum upon impact to the other car. the angle at which they strike and the relative velocities of each car dictate what direction and speed each car will be left with after the collision. Of course bumper cars have *bumpers* which absorb a great deal of the imparted momentum so the result is greatly reduced (wouldn't be much fun if they had steel bumpers! :-).

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 5


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QAId : 1108133
Asker : princegom
Subject : Help! Research!
Private : Yes

Question : Hi! I'm a San Francisco playwright, with a major play opening next year, funded by a grant from the Gerbode Foundation. I'd like to clarify a scientific concept as part of my research.

In the play, a character says she's writing a book about an invisible man. She asks a scientist how, in theory, would one go about becoming invisible. The scientist explains to her one possibility, in theory. I would like to know how accurate is the following dialogue:

----------

JULIE
Well, you see, human sight, all sight is only possible with the existence of light. So reflected or refracted light waves have to bounce off a person in order for the observer to see them. The light waves have to bounce off and hit the observer's retina. Now there are some electrons, free electrons, that will actually absorb all the light coming to it. These electrons will not reflect or refract light at all. So if you can find a way for this crazy scientist guy in your book to manipulate these electrons in some way so that they surround his entire body, I suppose he would be invisible to the human eye. In actuality, though, he's not invisible; he's just being blocked by these electrons.

GINA
So is there a way to manipulate these free electrons?

JULIE
I can't think of a way.

----------

Thanks, expert, for your help.

Prince Gomolvilas
Playwright-in-Residence
Lorraine Hansberry Theatre
San Francisco

Answer : This is not going ro ring as plausible for one very obvious reason:

If these so-called "free electron" do as described and absorb all the light striking them, the person will not be invisible, per se, but rather will be completely black, since no light from the volume of area they take up will reach an observer's eyes. The observer will see a shape of a person in complete darkness.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue
Rating : 5


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QAId : 1156267
Asker : deskeran@...
Subject : Reflection/Absorption/etc
Private : No

Question : Y'all,

I am unclear on certain aspects of the reflection and absorption of electromagnetic radiation. I'll briefly tell you what I do know (so you don't throw the basics at me that I already know) and then ask my question. I know that atoms absorb photons when that photon's energy matches a transition in that atom's electron energy levels. This energy is sometimes then emitted as another photon of the same energy (& color.) So an apple's pigments absorb and then immediately emit red, right? My question is about what causes transmittance as opposed to absorption. The apple apparently absorbs most other wavelenghts of light. Why does it absorb so much, and what happens to this absorbed energy? Why would this absorbed energy not be emitted as the electron returns to its ground state? What about a transparent, colored material--what is that doing? What about wax, which is colorless as a liquid and opaque white as a solid?Also, my understanding is that a mirror or other reflective surface is working the same way--a photon is absorbed and then another is released. How, then, is it "aimed" in the correct direction?

I know this is a lot; answer any or all of it that you care to. Thanks.

Answer : Sorry I took so long to get to this... I took myself off active status to take a break but it didn't "take" and your question slipped through - I had to go and take myself off active status again to get it to stick.

As for the question...

The rest of the light that strikes the apple (all but the red frequencies it re-emits) go into heating the apple. Those frequencies do not "resonate" with the electron orbits of the apples atoms and thereby only go into molecular motion.

As far as why some materials are transparent and allow transmission of light through them a transparent material appears as such because it's natural resonant frequency for photon absorbtion is higher than the frequencies of visible light. When an incident photon arrives in a transparent material the atom's electrons briefly absorb the photon. The electron then "plays" with the energy from the photon to discover if it's energy matches any of the states at which the electron can exist. This is called the "virtual state". If the energy matches, the electron absorbs the energy and may or may not ever re-emit the photon ("real state"). Most light is re-emitted and passed through the material after this brief playing, since most frequencies will not match the natural resonant frequencies within each atom type. This "playing" is why light is slowed during it's transmission through transparent materials. The higher the energy of the incident photons, and the closer they match the energy of the electrons playing with them, the longer the electron plays with the energy before passing it on. A transparent material would have a color like an orange does when illuminated with higher-energy photons that match it's quantum states (so the electrons of the material can permanantly absorb the incident photons - some to be re-emitted). Since this frequncy is outside our visual range we simply see the visible light that passes through the material.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue

Answer : In that last paragraph I noticed it might be implied that I meant to say that transparent materials would look like an orange, but in fact I merely was indicating that, like an orange (or any other normal material that absorbs most frequencies, while emitting the ones that grant it's appearance), transparent materials do this at a higher frequency range than for normal materials.

Answer : Don't forget to rate the answers you receive on AskMe.com.

Answer : Don't forget to rate the answers you receive on AskMe.com


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QAId : 1234347
Asker : Anonymous
Subject : center of gravity
Private : Yes

Question : How would you find the center of gravity of an object when the mass is not given only the dimension?

Answer : If you can assume the object is of uniform material you can hang the object by a plumb line (a string) twice from two different points and find where the paths of the lines through the object intersect. That is the center of mass for the object no matter it's shape.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue


Rating : 5


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QAId : 1241805
Asker : eugenes
Subject : justwannaknow
Private : Yes

Question : 1)can we travel through light?
2)what does radiation mean?
3)for the next few generationms,will be be metamophosized into some sort of mutant?
4)what happen if we get into black hole?

Answer : 1) Travel "through" light? I don't believe so, although "light" (radiation) can and does travel through us... X-Rays being a common example.

2) Radiation is a blanket term for any type of electromagnetic phenomena . ER (Electromagnetic Radiation) covers a broad spectrum of types of radiation, from infrared, radio waves and microwaves at the low-end to gamma and X-Rays at the high-end. Sandwiched in the middle of those is what we call "light" and are the visible wavelengths our eyes are attuned to.

3) Who can say what will happen, but if we were to have some (larger than usual) mutations I'd think it would take much more than a few generations to take hold. And that's assuming it's not
A) Fatal
B) Obvious so as to be easily avoided in offspring

4) If you enter a black hole you would be crushed by the gravitional field long before entering, and be reduced to your constituent parts (atoms) upon entering. After that, who knows? You might end up under a palm tree in Florida... :-)

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue


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QAId : 1241806
Asker : eugenes
Subject : justwannaknow
Private : Yes

Question : 1)can we travel through light?
2)what does radiation mean?
3)for the next few generationms,will be be metamophosized into some sort of mutant?
4)what happen if we get into black hole?

Answer : 1) Travel "through" light? I don't believe so, although "light" (radiation) can and does travel through us... X-Rays being a common example.

2) Radiation is a blanket term for any type of electromagnetic phenomena . ER (Electromagnetic Radiation) covers a broad spectrum of types of radiation, from infrared, radio waves and microwaves at the low-end to gamma and X-Rays at the high-end. Sandwiched in the middle of those is what we call "light" and are the visible wavelengths our eyes are attuned to.

3) Who can say what will happen, but if we were to have some (larger than usual) mutations I'd think it would take much more than a few generations to take hold. And that's assuming it's not
A) Fatal
B) Obvious so as to be easily avoided in offspring

4) If you enter a black hole you would be crushed by the gravitional field long before entering, and be reduced to your constituent parts (atoms) upon entering. After that, who knows? You might end up under a palm tree in Florida... :-)

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue


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QAId : 1277252
Asker : mrsbrantley
Subject : breaking boards
Private : No

Question : Dear PaulDoherty,

I have a question about "karate" boards. What would be easier to break when breaking multiple boards: 1) Two 1" boards held together so that there is no space inbetween.
or
2) Two 1" boards with spacers that separate the boards by say 1/4 to 1/2 inch?

Does the same rule apply as you add more boards say 3 or 4 boards?

This is a really old "arguement"....

Thanks:)

Answer : If this is a really old argument I'd say there are likely to be better answers than the off-the-cuff one I'm about to give...

My tendency would be to expect an easier time breaking the boards that have the space between them. Having the boards separated in this way would enable the first to be broken independent of the later board(s) since they are not touching. Additionally some of the momentum of hand could be maintained (with follow-through) and the pieces from the first broken board would be involved in breaking the next board down.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue

Answer : Don't forget to rate the asnwers you receive on AskMe.com.

FUQuestion : I think you're right, but what about adding boards to the stack, say 4 instead of 2? I would imagine this would be the same...isn't there some physics term for it...something to do with kinetic energy? I don't know I never got past chemistry...
Thanks

Answer : "Momentum" would be the word I'd apply. You're being allowed to conserve more of the initial momentum and break "parts" of the whole barrier, rather than having to sum up enough momentum to break all of them at once.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 5
Rating : 5


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QAId : 1279825
Asker : V_Ger
Subject : Quantum Computers
Private : No

Question : I recently heard of new device currently being researched at I beleive MIT. It is a Quantum Computer. The way it supposidly would operate is to analyze the spin of individual atoms (Their "Quantum State" I think the technical term is). The question I have to pose is this: Wouldn't the Heisenburg Uncertainty Principal prevent such a device to be constructed or operate correctly? Dare I make reference to Schrodinger's cat? :)

Answer : Hehe... I would tend to agree that trying to store or retrieve data from the *sub*-atomic realms could be difficult, but it sounds like they are using the atom as a whole, which is less of a bondary due to it's larger size (well, larger than an individual electron anyway).

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 4


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QAId : 1289774
Asker : cheernbabe02
Subject : Egg drop
Private : No

Question : Hello, for my physics class we need to make a holder for an egg drop of 15 feet. We can use 5 pieces of computer paper and 1 meter of masking tape. Do you have any ideas?

Answer : The best thing I can think of would be to conctruct either tails or a parachute (depending on how thing you can tear the strips) attached to the small rear of the egg amd use at least one piece of paper as a rolled-up cushion at the larger end. The tail or shute will help align the egg so it hits on the end (an egg is strongest in this up-down direction - try squeezing one and see) and the chute or tails will help decrease the speed of the fall from wind resistance.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1304109
Asker : mylittlechicken3
Subject : physics in architecture
Private : No

Question : How are physics used in architecture? If you could just give me an overview of this it would be very much appreciated. Thanks.

Answer : Architecure (and engineering in general) is like the "art" of physics. It is a physical manifestation of the principles of physics. So if I had to say what principle of physics architecture exemplifies I'd have to say it is Newton's law "for every action there is an equal but opposite reaction". The whole (functional) idea behind a building is to make a contrivance that will hold itself up against gravity. The whole design of the infrastructure of the building is carefully designed to distribute stress and maximize usable space. We've gotten so good at it and have such strong materials that aesthetics come into the picture and the buildings can be beautiful as well as functional.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue


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QAId : 1318642
Asker : robbieg211
Subject : Physics and Surfing
Private : No

Question : I am doing a Science Project on the Physics of Surfing and I was wondering if you could answer my questiongs.
1) What is the relationship between Vectors and Surfing?
2) Why does a person go faster is riding the wave on the side or at an angle then when he goes straight in front of the wave?

Thanks For your help. Answer what you can.

Answer : Vectors would be involved (as always in matters of motion) insomuch as the surfers' final direction of travel is a combination of the vector of movement imparted to him by the wave and the vector dictated by the angle of attack of his surfboard.

Now as for you travelling faster when not following the same path as the wave. When you go in the same direction as the wave the distance travelled and speed must by definition be the same since it't the wave that is impelling your movement in the first place. When you travel at an angle to the direction of the wave you will traverse a greater *distance* than the straight perpendicular line from wave to shore but you will stay at the forefront of the wave. the result is that you will travel away from the perpendicular of the wave yet stay even with it (as you "fall down the front of the wave") so you have travelled a further distance in the same time. Draw this on a piece of paper with the wave being a long flat line, and the normal ("straight-ahead") surfer moving in the same direction. It's easy to see that the surfer covers the same distance as the wave and so their speeds are the same. Now draw another line representing the surfer travelling along the wave at a 20-degree angle or so from perpendicular. You will see that a triangle is formed between where each surfer began (current wave position), where they each end up after any given period of time, and where the wave will be at the end of that same time period (both surfers will be laterally still in line with each other and the wave). It is apparent then that the "angle-surfer" has travelled a greater distance in the same time so his speed was faster. As you can then plainly see the triangle formed is a right-triangle and you can use Pythagoreus's theorem to determine the distance the "angle-surfer" travelled compared to the wave and straight-ahead surfer. (a^2 + b^2 = c^2).

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1319814
Asker : nietos
Subject : forces
Private : No

Question : According to my teacher, there are four types of forces in the universe that control how everything behaves. What are these four forces?

Thanks,
F

Answer : The four forces your teacher is referencing are likely:

gravity
electro-magnetic force
weak nuclear force
strong nuclear force

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue


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QAId : 1331650
Asker : Anonymous
Subject : Center of gravity
Private : Yes

Question : Please... I have no idea how to find the center of gravity of an object that is like this...

the "*" are just spaces so pretend they aren't there

4 meters wide
___________
|*********|
|*********|2 meters long
|*________|
|*|
|*|2 meters long and 1 meter wide
|*|_______
|_________|1 meter long

Answer : Hanging any object from two or more points by a string will show you (by drawing a line through the object towards the ground) the object's center of mass. The point where the two different hanging points lines toward ground intersect is the center of mass.

For the math-based method (for imaginary objects you don't actually have to conduct the direct method with above):

http://www.math.wpi.edu/Course_Materials/MA1022A99/center_of_mass/node1.html

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue

FUQuestion : So how would I answer the question?

Answer : Is this homework? I don't answer people's homework for them (and in this case I don't know the formula - weren't you given the formula with the assignment?).

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue

Answer : If you *were* given the formula I'd be interested to know what it is... and could assist you in working it out.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue

FUQuestion : there is no equation given and its not a homework problem. I'm not even in school. It was just a question I can figure out

Answer : Oh ok...

Well in this case it appears that without having the actual object in-hand (in which case you could conduct the experiment I suggested in my first response) you would have to employ some ugly calculus. The details of which are in that URL I put in the first response.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue


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QAId : 1341229
Asker : Anonymous
Subject : Waves
Private : No

Question : Hi Hi! I'm very interest in this science, so i want to learn more about the physics. I hear my friend which studying Physics told me that they are learning waves. B/c i don't have time to take Physics this year. So i have no idea where i can find the answer to my question. I know the meaning of speed and amplitude, but i want to know that is amplitude depend on speed?

Answer : You're a bit confused - let's see if I can help. Speed of a wave is a function of two simple items - frequency and wavelength. Frequency is how many times a wave oscillates per second, and wavelength is the distance between identical portions of the waveform. If you multiply the frequency times the wavelength (distance travelled per oscillation) you will get the speed of the wave's travel.

Amplitude is an unrelated term that refers to how far above or below a "zero" value a wave is at any particular moment. The easist analogy is sound. A loud sound has a higher wave crest than a softer sound - we would then say the amplitude of a loud sound is higher than for the softer sound.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 4.8
Rating : 4.8


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QAId : 1678904
Asker : Echang14
Subject : Effects of Gravity
Private : No

Question : I have a project to construct a device that will protect an egg that is dropped off of a two story building. I am suppose to use my knowledge of physics to counter the effects of gravity upon my egg.
These are the materials allowed:
Up to 150 soda straws, tape, string, propellers, rubber bands, glue, wire, wood and cylafang.
The teacher said that we couldn't wrap 50inches of tape around it to prevent the egg from breaking. He also said that the egg must be visible (not totally covered and protected). Also, no parachutges or balloons or cords are allowed. The device must impact the ground also.
I need an idea to maybe get started.
I figured out that i could probably slow it down using propeller with rubber bands, but this doesn't save my egg from cracking or breaking.
What suggestions do you have?
Thank you.

Answer : I would probably build a cage out of the soda straws and suspend the egg inside it (towards the top) with the rubber bands.

Or use the 150 soda straws arranged in a circular fashion around the heavy end of the egg (when viewed from the side picture the egg upright with a large 'X' of soda straws supporting it) - if you can fashion a grouge chute (anything attached to the back to create drag) you can slow the descent slightly and force the egg to stay facing down as it falls.

Good luck!

Paul Doherty
http://members.home.net/iqueue

FUQuestion : how do i suspend the egg in the middle?

Answer : With the rubberbands was how I was picturing it - the actual logistics will have to be worked out by you, I was just trying to forulate a plan.

Paul Doherty
http://members.home.net/iqueue
Rating : 3


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QAId : 1702816
Asker : JackofAllTrades
Subject : Ski length and ski wax vs speed
Private : No

Question : This is a two part question.

First, Why do you go down hill faster on longer skis? Is it because you can ride out the tiny bumps better; or because more of the snow will become water under the ski, thus less friction; or something else altogether?

Second, Why does ski wax make you go faster? If you run your hands through freshly waxed skis, it seems to have more friction.

This is part of ongoing arguments I have been having with my friends for awhile.

TIA,

Answer : My quick answer would be to say that the process of snow skiing is very similar to that of ice skating, in that you are indeed travelling over a thin surface of melted ice (or snow). This process is called 'regelation'. In the case of a longer ski (assuming width is a constant between the ski types) you may melt less ice/snow with the longer ski due to the increased surface area (and corresponding lower pressure per unit of surface area). Here is a conversation by some skiers that is fun but doesn't shed much light on the subject - click "next in thread" to read on...

http://x55.deja.com/getdoc.xp?AN=587333646&search=thread&CONTEXT=962549340.1485963300&HIT_CONTEXT=962549303.1484259547&HIT_NUM=&hitnum=2

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1754356
Asker : Anonymous
Subject : How do sound (and radio) waves travel?
Private : No

Question : I understand that a wave must have a medium to travel through (it can't travel through a vacumm)as it's the vibration of molecule that carry the wave. I assume that each molecule knocks in to the next one, passing on energy, which causes that to vibrate and so on. I also assume that on each 'knock' energy is lost, until the energy is so small that the wave can not be detected.
Sound waves travel in the audiable spectrum, radio is a sound wave that is added to a carrier wave which is outside of the audibility and then the radio receiver converts this back to audible sounds when it receives it. Each radio station uses a different frequency carrier wave.
(1)How do all these different frequencies (sound, radio, TV, mobile phone) travel? (2)How do molecules vibrate at all of these frequecies at the same time? (3)Are we constantly surrounded by molecules vibrating as a result of radio / TV / Mobile phone? (4)Do any of the molecules in our bodies vibrate due to these waves?
Hope there aren't too many question there for you.

Answer : The main thing you are missing here is that of the phenomena you are discussing only one is a physical wave - sound. Radio waves, microwaves (mobile phones), and television are all signals carried on *electromagnetic waves*. Electromagnetic radiation is a form of pure energy and requires no medium for transmission (infact mediums just get in the way - that's why light from the sun is slowed slightly and bent by the air in our atmosphere or by water when looking into a pool or bathtub).

As far as the molecules of your body oscillating in rhythm to some of these frequencies of radiation I'd have to say that yes some do. And some frequencies are more powerful than others - some of which can cause cell damage and our not so nice friend, cancer.

I hope that answered your question(s)...

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 4

FUQuestion : So are radio waves etc classed as 'light' waves?
How does this energy travel from one place to another?

Answer : Yes, radio waves are the same phenomenon as visible light - just of a longer wavelength. It is pure energy (as opposed to a mechanical vibration such as sound waves, which are truly defined by their medium) which is why is needs no transmission medium. Sunlight is a perfect example - it is a mishmash of ER frequencies and travels a vast distance to arrive at Earth in the same form it was when is was emitted.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue

FUQuestion : Paul,

You refer to Radio (and light) waves as pure energy, but what is pure energy? and where does this energy come from?

Regards,

Richard.

Answer : The energy can come from heat, motion, electrical or magnetic forces, or from other sources of ER.

When an atom becomes excited, by physical or electrical means, it's electrons become elevated to levels above their normal orbits. These electrons then drop back to their normal unexcited state and in the process give off the energy they gained. Since the orbits are at definite levels apart from each other, and since the electrons cannot reside between these levels, the energy given off by an electron going through this de-excitation process is said to be quantized. Quantization in this usage means that the energy is given off in discrete steps of energy. This excitation and atomic quantization is where we get some of the things familiar to us. As you probably already know electromagnetic radiation (I'll call it ER from here on out) in the ranges that our eyes use is generally called "light". So light is produced by this same mechanism - electrons get excited up to a higher-than-normal orbit, and then de-excite, giving off the energy they had gained in the form of a photon (quantized "piece" of ER).

Here's a good example of the quantization of light. I'm sure you've seen the so-called neon signs in convenience stores and such? Those signs are an excellent example of the quantized nature of electron orbits. Those lamps contain a pure gas - in the case of the bright red ones it's neon. The particular combination of electron excitation/de-excitation steps available to the neon atoms is what gives neon it's characteristic red color. Argon is another gas used in these lights and has a blue color for the same reason. Each type of gas has it's own characteristic pattern of available electron orbit hops that give it unique color. Contrast these types of lights with an incandescent light like in your house or on your car. These use a metal filament which when heated glows and gives off light. the same process if happening as in the gas but we get (closer to) pure white light from this type of bulb. Why? It's because now, instead of the limited nmber of combinations of electron orbit hops we had with a gas (where atoms are relatively far apart), we have a solid material with atoms shoved close together. The result being that electrons who make a hop to higher energy orbit in one atom may very well de-excite into a nearby atom making the energy patterns closer to infinite which also makes the frequencies of emitted ER nearly infinite - white light. A flourescent bulb works like a neon light but produces white light. How is that? It uses mercury vapor inside the tube, which when a current is passed through excites and gives off the standard limited number of patterns a gas can produce. But this light isn't even visible - it's ultraviolet in frequency. the white light actually comes from the spray coating on the inside of the tube - this solid material absorbs, and becomes excited by, the UV light and in turn gives off it's own less-limited pattern of white-ish light.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.Sc.
http://members.home.net/iqueue

FUQuestion : Paul,

Thanks for all your answers. They are very interesting. Hope you don't mind me answering so many follow up questions. Please let me know if you do.

I think that I understand how light works now, however could you tell me if I'm on the right track.
I have number my questions and assumptions so that it is easier for you to reply.

Atoms in a light bulb are excited by electricity which causes their electrons to move into a higher orbit. When they fall back to their original orbit they give out energy [photon]. (1)I assume that in the sun this is caused by a chemical reaction(?). We see objects because light [photons] bounces off them and are then enter our eye which the brain interpretates.(2) Do the photons actually 'bounce' or does the photon that hits the object cause a new photon to be omitted? (3) I assume that we see colour because a red object only reflects red light, a yellow object only yellow light etc.
(4) So if I have the above right, then an objects colour depends on the different atoms within an object. Each different atom emits a different amount of red or blue or green which 'combine' to produce the final colour.
(5) If a near infinite number of photons are travelling in all direction all of the time, then do these photon colide and if so what happens?

The different colours (different frequencies of photons) that we see are due to different atoms having different distances that their electrons travel between the normal and excited state. Going back to one of my first topics, (6) how are radio waves created? I appreciate that these 'waves' are just photons with a different frequency (energy level) but how does a transmitter create them?

Thanks again for your answers.
Regards,
Richard.

Answer : 1. In the sun light is generated as mass is *directly* converted to energy from mass. The sun is a huge nuclear fusion reactor, turning hydrogen atoms into helium and other light elements. The disparity between the mass-per-nucleon (namely the huge reduction in MPN going from hydrogen to helium) is where this ER and heat come from.

2. Photons are "re-emitted" - the mass that makes up any object can be thought of as being "in tune with" certain frequencies of light, much like a tuning fork. If you shine white light on the object all frequencies are absorbed as heat except the ones to which the material is "resonant". The resonant ones energy goes into the elevating into higher orbits and re-emission of another photon.

3. Yes... Answered in #2 above.

4. The object re-emits those frequencies to which it is attuned.

5. Light travels and interacts both as a wave (like gravity or magnetism) *and* as a particle. This is one of the great apparent paradoxes of light. So I would say that interference patterns would be the result, with constructive and destructive interference the result. But I can not definitively state this without research and I haven't the time to do so tonight.

6. As for how a radio transmitter works here is a good description of the rapid oscillating electric charges that run up and down the antenna:

"Electromagnetic waves are created whenever electrically charged particles change speed or direction; whenever they accelerate. Since there are accelerating electric charges everywhere--thermal energy keeps them moving about--there are also electromagnetic waves everywhere. But the radio waves used in communications systems are generated deliberately by moving electric charges back and forth. When charges are sent up and down a radio antenna, these charges are accelerating and they form complicated electric and magnetic fields that include electromagnetic waves. Once launched, those electromagnetic waves propagate through space at approximately the speed of light."

A radio station launches a radio wave by moving electric charges rhythmically up and down their antenna. As this electric charge accelerates back and forth, it produces a changing electric field--a structure in space that pushes on electric charges--and a changing magnetic field--a structure in space that pushes on magnetic poles. Because the electric field changes with time, it creates the magnetic field and because the magnetic field changes with time, it creates the electric field. The two travel off across space as a pair, endlessly recreating one another in an electromagnetic wave that will continue to the ends of the universe. However, when this wave encounters the antenna of your radio, its electric field begins to push electric charges up and down on that antenna. Your radio senses this motion of electric charges and thus detects the passing radio wave.

And continuing...

"To convey audio information (sound) to you radio, the radio station makes one of several changes to the radio wave it transmits. In the AM or Amplitude Modulation technique, it adjusts the amount of charge it moves up and down its antenna, and hence the strength of its radio wave, in order to signal which way to move the speaker of your radio. These movements of the speaker are what cause your radio to emit sound. In the FM or Frequency Modulation technique, the radio station adjusts the precise frequency at which it moves charge up and down its antenna. Your radio senses these slight changes in frequency and moves its speaker accordingly."

The last gleaned from the website:

http://rabi.phys.virginia.edu/HTW//

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities





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QAId : 1754417
Asker : Anonymous
Subject : How do sound (and radio) waves travel?
Private : No

Question : I understand that a wave must have a medium to travel through (it can't travel through a vacumm)as it's the vibration of molecule that carry the wave. I assume that each molecule knocks in to the next one, passing on energy, which causes that to vibrate and so on. I also assume that on each 'knock' energy is lost, until the energy is so small that the wave can not be detected.
Sound waves travel in the audiable spectrum, radio is a sound wave that is added to a carrier wave which is outside of the audibility and then the radio receiver converts this back to audible sounds when it receives it. Each radio station uses a different frequency carrier wave.
(1)How do all these different frequencies (sound, radio, TV, mobile phone) travel? (2)How do molecules vibrate at all of these frequecies at the same time? (3)Are we constantly surrounded by molecules vibrating as a result of radio / TV / Mobile phone? (4)Do any of the molecules in our bodies vibrate due to these waves?
Hope there aren't too many question there for you.

Answer : The main thing you are missing here is that of the phenomena you are discussing only one is a physical wave - sound. Radio waves, microwaves (mobile phones), and television are all signals carried on *electromagnetic waves*. Electromagnetic radiation is a form of pure energy and requires no medium for transmission (infact mediums just get in the way - that's why light from the sun is slowed slightly and bent by the air in our atmosphere or by water when looking into a pool or bathtub).

As far as the molecules of your body oscillating in rhythm to some of these frequencies of radiation I'd have to say that yes some do. And some frequencies are more powerful than others - some of which can cause cell damage and our not so nice friend, cancer.

I hope that answered your question(s)...

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue

Answer : Don't forget to rate the answers you receive on AskMe.com

Answer : Ignore that reminder to rate the answer - I didn't remember that this question was accidentally asked twice.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 4


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QAId : 1771689
Asker : Anonymous
Subject : acceleration, velocity and gravity.
Private : No

Question : How do I calculate the speed of an object falling from a 10 story building on earth. Does the weight of the object matter? Is the gravitational pull 32ft.sec.sqrd., the same everywhere on earth? Can you provide a sample equation? Thank you.

Answer : I believe the speed would be:

gt^2

where g is 9.8 m/sec and t is time in seconds.

So an object (of any weight) after falling for 5 seconds would be at a speed of:

9.8 * 5^2

9.8 * 25 = 49 m/sec

Of course the weight of the object *does* matter after only a few seconds of fall (or perhaps even before if it's light enough) due to the air that makes up our atmosphere. Wind resistance will retard the acceleration and make objects have different terminal velocities (fastest speed of freefall). For instance a bowling ball and another ball of identical shape but made of stryofoam will have dramatically different terminal velocities. Each accelerates to the point where wind encountered as resistance equals the weight of the object. Since the bowling ball is much heavier but has identical surface area and volume it will fall much faster before wind resistance can equal it's weight.

As for your question regarding acceleration at all parts of the Earth - 9.8 m/sec is more of an average and it does vary based on how far from the Earth's surface you are when you measure it. Gravitational pull falls off as an inverse square (which just means flip the distance difference over and you have what is left in gravitational pull). For example at a distance X a gravitational pull of Y is measured. If we triple X (the distance between the bodies) and now measure we should see:

Y/9

3 times the distance ^ 2 = 9

So the force is now only 1/9 what it was before. So this same effect occurs to smaller degree on Earth - on top of a mountain you weigh less and experience a slightly slower acceleration speed due to gravity than at sea level.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1779028
Asker : tjdusdl
Subject : Physics experiment
Private : No

Question : Hi! pauldoherty
I am Korean high school student who study in the
Philippines.
I have a very importent project...
I have to make my own experiment about physics.
I don't know anything about physics and since you are
great expert on that field i am asking you
favor.
Could you please recomend a great experiment
stable for high school student?
It would be better if it's related with accerelation or vector.......
cause it is our topic nowadays.
Any way, I am sure you can give really great
answer
If possible could you list down the materials
for that experiment and also 1general objective and 2-3 specific objective..?
I think you can easily help me..
Thank you very much

Answer : I found a site that has several excellent examples with full details and procedures. I'm sure this will adequately answer what would take me a few pages to do, and you'll have several to chose from - good luck and have fun!

http://sprott.physics.wisc.edu/demobook/intro.htm

Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1784331
Asker : davem
Subject : Inverse Square Law
Private : No

Question : How would I properly use 1/d^2 to measure gravity and magnetic fields? This would primarily be with gravity and magnetics working together, if that makes any sense.

Answer : Both gravitational and magnetic fields operate on the inverse square law. To use this to measure (or predict) the strength of either you can (example of gravity):

1) Measure the distance between the attracting bodies.

2) Measure the attractive force (or acceleration experienced).

3) Now you can use the inverse square formula to predict what the force will be at any distance - if you double the distance (between the objects) you used in steps 1 & 2 you will now be at 1/4 the gravitational force. If you now make the distance only 1/3 of what it was in steps 1 & 2 the force will now be 9 times as strong, and so on.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1798273
Asker : skipagen
Subject : The "heavy ball"
Private : No

Question : I asked this of a Physicist on page one and he didn't know. So here I go again.

Is there such a thing as that 'heavy ball' we hear about of certain baseball pitchers (and now, during Wimbledon, of a few tennis players).

It's a very vague thing. As far as I can tell, the tennis explanation of this phenomenon would go something like so:

Two guys hit a tennis ball at 120 mph.
Let's say you just try to block the shot back. Holding the racket firmly, you simply put the racket head perpendicular to the line of flight and the ball bounces off of it and directly back over the net.

With the light hitter, you experience no reaction. With the heavy ball your racket gives. You can see and feel it rebound under the force. (I know, I know, my terms stink, but this is the way they descibe things.)

In baseball the idea is similar.

Two guys throw fastballs at 95mph. One throws a "light ball" (if there is such a thing), the other a "heavy ball."

Catching the latter is supposed to be wearing. If the catcher snags the ball right in the pocket (as opposed to in the webbing) of the mitt, the ball seems to have more bite, drilling or grinding itself into the glove, hurting the catcher's hand.

My question: is there any truth to this stuff? If yes, what's the cause?

Does the heavy-baller impart more spin which provides the additional bite?

Or is it all just more baseball BS and the reality is the heavy baller simply throws faster, and to hell with the radar gun readouts?

I hope to hear from you.

Skip Agen

Answer : I'm going to have to side against cultural myth in this case. If the balls both measure to be the same speed and direction (sans spin, which may have an impact on the force felt with the baseball or the ability to return the ball if we're talking tennis) then their momentum is identical. Therefore the force felt in both cases is the same.

Possible explanations for a difference (using tennins as an example) in the numbers of returned shots could be:

1) Statistical anomoly that will average out over a large number of games (I find this to be unlikely, however since for this to have become a myth there must be some people who can consistently exhibit these "unhittable" shots)

2) Timing - the person who can perform these shots may have an almost subconscious ability to time their shots so that they arrive when their opponent is least prepared to receive them, catching them at their weakest, or "off-balance". This, or the ability to deliver shots in a deceptive way (deliver shots that are not anticipated, be they strong or weak, and where they land/spin/etc) could also complement this idea.

3) Attitude - psychological intimidation and reputation can be powerful forces that may set an opponent up to "expect" to have a hard time with a particular player. This in itself could account for the entire phenomenon.

Paul Doherty, CNA, CNE, MCP+I, MCSE, B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1804597
Asker : Anonymous
Subject : Newton Law
Private : Yes

Question : Would you discuss the concept of gravity, and explan newton law of universal gravition in detail?

Thanks

Answer : As you already know gravity is simply the attractive force that exists between all bodies of any mass whatsoever. The strength of the pull depends on:

1) The masses of the objects in question.

2) Their distance relative to each other.

Newtons' Universal Law of Gravitation was the first theory to state that the force that makes an object fall on Earth (his favorite was, of course, the apple) is the same as the force that makes the moon orbit the Earth, and the Earth orbit the Sun. Prior to this time it was believed that there were at least two sets of forces - one for Earthly events and one for Heavenly ones (planets and stars).

Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1848475
Asker : Anonymous
Subject : If......
Private : No

Question : Dear pauldoherty,
If a larger object is dropped inside a glass of water, will I see bigger bubbles?
Anonymous

Answer : I would say yes, for the simple reason that (depending on mass (which will in turn dictate rate of descent into the water)) a larger object of the same density and shape as a smaller object displaces a larger volume of liquid. This generates a larger *initial* bubble as air following the object (Bernoulli at work here) into the water gets encapsulated by the water and then rises.

Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Rating : 5


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QAId : 1860900
Asker : Anonymous
Subject : Wave motion
Private : No

Question : AM radio signals can usually be heard behind a hill, but FM often cannot. Please help me explain it

Answer : I believe this would be due to the fact that AM radio waves are of a lower frequency (and corresponding longer wavelength) so the AM waves can "bend" around obstacles better, as well as be reflected by the atmosphere (why you can pick up AM stations from farther away than same-powered FM stations - the shorter-wavelength FM signals pass through the atmosphere into space rather than be reflected back towards Earth).

Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue

Answer : Don't forget to rate the answers you receive on AskMe.com

Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Rating : 4


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QAId : 2187539
Asker : Grouchy567
Subject : Interference of light
Private : No

Question : Why do CD's show colors when you tilt the disk? I suspect it is due to interference of light, but what is the cause of the interference? I have heard an answer that referred to "pits" in the CD disk, but don't understand how they would cause the interference color patterns (if indeed that is why the colors appear)

Answer : You are correct - this effect is called "thin-film interference" and comes about when the reflective surface is either covered with an irregular-thickness covering or (in this case) the indicent angle of light causes each "ray" of light that eventually strikes your eye to pass through different thicknesses of the plastic layer on a CD. When the light is reflected off the shiny surface inside the CD some of those reflections meet with opposition (if the density of the material is complementary to the wavelength of the light) in the form of internal reflections off the inside of the clear plastic on the CD. This "destructive interference" can cause the removal of frequencies (for example yellow light may get destructively removed, leaving it's complement, blue.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 2229625
Asker : edm_m@...
Subject : speed of light
Private : No

Question : hi,
my brother and i are fighting over the fastest speed. I say it the speed of light and nothing is faster, but my bro says there is something faster.
so i wanna know if there is something faster then the speed of light to end our dispute and prove him wrong.

thank you.

Answer : I will side with you on this one - there are some people working on proving that there are faster-than-light particles (like tachyons) and such, but I'm toeing the "light is the fastest interaction" since I've not been introduced to anything compelling to convince me otherwise.

Here is some information that may help mollify your brother about the recent tests by NEC that showed faster-than-light transmission for light itself (but still had light-speed as an information-exchange maximum):

http://x66.deja.com/threadmsg_ct.xp?AN=650320714.1&mhitnum=0&CONTEXT=964905369.1587216409

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...



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QAId : 2243498
Asker : jtaber
Subject : Magnetism
Private : No

Question : When a bar magnetic is stuck on to iron, what prevents the unpaired electrons in the iron from being stripped from the iron nucleus by the magnetic pull?

Answer : Magnets work because the inner portions of them (called "magnetic domains") are in alignment. Domains can be thought of as the smallest magnets possible (like a "magnet molecule", if you will) with a north and south pole - a magnetic material differs from other metallic non-metallic materials in that the domains are (mostly) all aligned in the same direction which is what creates their north and south poles with each domain amplifying the field of the other domains around it. These domains are the reason why you can break a magnet into any number of smaller pieces and the pieces themselves are still magnets (although physical shock and heat are two enemies of magnets that can decrease the effectiveness of a magnet by randomizing the arrangement of the domains so that some are now "misaligned" and no longer count directly towards the overall strength of the magnet). These domains can be brought into line at least temporarily by proximity to real magnets. A good example is an experiment to create a compass. To do so you need a small glass of water, a small cupped tree leaf, a needle and a magnet. Then by stroking the needle with the magnet you can align it's domains and make the needle into a relatively weak magnet. Then you place the leaf on the water (so it's floating on the surface) and place the needle on top of the leaf. The new magnetized needle will produce a torque on the leaf, and since the leaf is on a relatively frictionless surface (water), the needle/leaf combination will rotate to align itself with magnetic north.

As for your mention of electrons and iron - the iron atoms would not be stripped of their electrons primarily due to the fact that electrons are *electrically* charged, and are not magnetically attracted to either pole of a magnetic material (and the other reason being that they are held in place by a stronger electrical pull from the nearer-by nucleus which contains the oppositely-charged protons).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 4


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QAId : 2246216
Asker : gnoroian
Subject : sound
Private : No

Question : can you give me the equation for determining sound speed, such as elevation. im interested in making a graph. Or could you give me a site that has this information.

thanks

Answer : Here you go - an online speed of sound calculator!

http://www.digitaldutch.com/atmoscalc/

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 1


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QAId : 2329321
Asker : awais
Subject : spectrum of light
Private : No

Question : sir,

1) generally when light is allowed to fall on prism it splits up into seven colors and these colors are obtained on the screen but when rainbow is formed there is no screen on the sky
then how we see it

2)like charges repell each other but in the nucleous of an atom there are protons all positive then why dont they repell and go out of it same is the case with the electros

yours faithfully
awais

Answer : We see rainbows only under the circumstance that there is sunlight (or other near-white light source) behind us and rain (or other source of water vapor like a sprinkler) in front of us. The light rays are refracted (and internally reflected) inside the drops of water and this is what produces the same effect as a prism, the differing angles from your eye, to the sky, to the light source, determining what frequencies will appear where (with each frequency being bent at it's respective angles).


The force that bonds the nucleus together, even though there are large repulsive forces between the protons is called the "nuclear force". It acts only over very short distances and bonds nucleons together. This repulsion (and the need for close proximity to bring nucleons together) are factors in why nuclear fusion is so hard to produce - it requires massive heat to get the protons to travel fast enough that they might overcome their repulsive forces to come close enough to be captured into one nucleus (thus forming another element).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



Rating : 5


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QAId : 2389719
Asker : w_bressler
Subject : Two cards,Two machines, One Driver under Linux
Private : No

Question : I have Two computers; an HP Vectra VL2 4/33se, and an Compaq Presario 7360. I also have Two Ethernet cards; in the HP I have a Kingston KNE-20BT and in the Compaq I have a Linksys 10/100 network card. According to all of the Linux documentation that I have reviewed so far indicate that BOTH cards are supported by the same driver, a tulip driver. When I do a check of the I/O addresses of the card, I get the same addresses as I would if I looked them up under DOS, and (again) apparently, according to the docs, this numbering system is not compatable under the Linux OS. (ex. 003fh for DOS, as compared to 0x350 under Linux). So, my question is how, under linux, do I obtain the (linux) correct addresses for my cards. ( I am only having this problem on my Compaq, however, there is no OS on my HP so I have NO CLUE about setting the card up on that machine ). If I select PLIP on my HP and go through the "automatically probe" sequence a time or two, then the machine(HP) goes ahead and starts asking for my Network information ie.,Hostname,Domainname,..etc.. So, I don't know if the card on that one is working untill I get the card on my Compaq going, because I am trying to load the operating system to my HP through NFS (I boot from a networking boot disk on my HP ) so that I can avoid two problems; one, take both machines apart and use the (Compaq) CDROM to boot the entire system onto my HP, or,two,use multiple floppy disks. Besides, I need to be able to connect the two boxes anyway,( I NEED A NETWORK ) because after that I will connect yet another computer to the network, so, I might as well get everything figured out now. If there is any way that you can help me (even if you have to referr me to someone else) I would be very gratefull. I just can't go any farther without help. If the answer is long and complicated I would be glad to give you my e-mail address so that you (maybe) wouldn't have to try to post it here, (not that I mind at all). Thanking you in advance; Thanks!

Answer : The difference in the hex values between DOS and Linux is probably the difference between where the card is actually *at* (DOS) and where Linux will first default to *probe at*. In both cases the address should be the same - so if you can confirm that the address is indeed 0x003f then you can input that value when asked in Linux (or let it probe as you mentioned). One way to confirm the driver was loaded during the install of Linux is to try ALT-F2 through ALT-F9 and see if you can find the console where the driver was actually loaded - there will be some text indicating the success of the driver loading.

If the auto probes don't end up working for you under Linux you may need to dig out the floppies that came with each network card - almost always there is a utility on there (SETUP.EXE usually, but not always). This utility will allow you to dtermine definitively the I/O address (the values you were citing) and the IRQ of each card. You can then note these and use them under Linux.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : I do have a floppy with a driver for Linux, however, I don't know anything about compiling drivers or loading modules,etc. I can get Linux to mount a floppy, but that's about it. I know this only because if I type "mount fd0" then I can see the floppy drive light light up. However, I know very little about where to put a file like that, and/or "compile it", which I gather I'll have to do according to the readme file on the floppy(Linksys floppy). I tried the commands listed on the floppy but they didn't appear to work, but then, how in the heck would I know? This is not ANYTHING like Windows! Which, if you're willing to work with me a little, I have a Problem with Xwindows too :=). However, getting my network up and running is my first and foremost concern. Willing to go the Xtra mile?

Answer : You won't need to compile it... the drivers for your network card are likely already in place - just select them and use the values for I/O and IRQ from the DOS utility I suggested you run *from DOS*. That's all you need - no special steps should be required. Select the "tulip" drive you mentioned.

About X - don't get your hopes up... one thing at a time... :-)

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...

FUQuestion : O.K. I got my Kingston ethercard going by inserting a boot floppy from Windows and copying a Linux Boot image onto the hard drive and then,using a Linux boot floppy to do a Network download. When prompted for the ethernet card, I used each card ( only the ones that I figured would work with a Kingston card )and repeatedly entered different I/O addresses at each prompt. I only went through two cards, but I had to repeat the I.O's about fifteen times on the first; then when I figured the card wasn't going to work, I switched to the second, and , bingo, after the third try,(I/O 0x240), it prompted me for the network info. However, I have not had the same success with my Linksys card. For one, I can't get my Compaq to go through the same proceedure as the HP Vectra; (I don't know why) it will not do a network boot. In fact, the bootdisk doesn't even work on the Compaq.It keeps coming up with "boot failed". And that's the bootdisk that I created on installation! So, I used the Tulip driver on the Compaq but it just makes the hub light go out, but everything else appears to go o.k. during boot. There are no error messages, such as " failed to initialize eth0 ". However, when I do " ifconfig " it does say that the Network is unreachable " and " no such device ", even when I used the I/O addresses that I got from Windows and the floppy that came with the card (the diagnostic program, which was no help at all, except to verify that the Windows information was the same). Although there is one difference when I use the I/O addresses from the Win program; the difference is that the hub light does not go out. But then, the hub light doesn't go out when I try other drivers either. I have recompiled the kernel to use BIOS settings to detect the card; I have loaded about ALL of the drivers one-by-one,(just on the off chance that another driver might work), all to no avail. I can't remember exactly WHERE I read this, but I read in some of the Linux documentation that Linux might detect the cards backwards, but I don't think that this is happening; but, then, I don't know for sure that it's not. This card is giving me a fit! I have spent three weeks now (from 10:am-2 or 3:30 am)trying to make this card work. Where can I get some REALLY GOOD diagnostic tools (and, "not-too-complicated" instructions on how to use them)? I have a great amount of confidence that you'll be able to help me, and I appreciate your help so very much. Looking forward to your next reply. W_B

Answer : You've gone through a lot already - perhaps it's time to see if another distro can help (or perhaps a minor expenditure of 20 dollars for newer ethernet card may be in order). Mandrake Linux 7.1 (http://www.mandrake.org) has a "plug and play-ish" hardware detector that may find the card and install the right driver. Have you gone out and found a Linux driver specifically for this other NIC? If you really want to continue the pain here are some sites with Linux apps that may help you:

http://freshmeat.net/appindex/
http://www.linux.org

Perhaps re-reading our discussion(s) above may help you too...

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities


Rating : 4
End :


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QAId : 2400368
Asker : Anonymous
Subject : critical angle
Private : No

Question : what is the definition of critical angle?

Answer : The critical angle is the incident angle to a refractive plane at which all of the incident light is internally reflected. Now in English...

Imagine you have a waterproof flashlight and you are using it in the bathtub filled with water. If you point the flashlight straight up the light passes right out of the water without bending and strikes the ceiling above. If you now start to angle the flashlight away from this vertical line (which was perpendicular to the water surface) you will now start to see some of the effects of refraction (the effect in the event of the perfectly perpendicular was simply a slowing of the *entire* wavefront, rather than one edge of it more so than the other which is the standard case for what we think of as "refraction"). The effect you will see is that the flashlight will now strike a place on the wall lower than where you are actually aiming as the "top-most" edge of the wavefront strikes the air first and speeds up, bending the angle that the light travels at to make it end up lower of the wall than the initial angle of the flashlight would indicate. As you continue to increase the angle away from perpendicular you will find that a portion of the light is longer being transmitted through the water/air barrier and is instead being reflected back into the tub. This effect will increase as you increase your angle away from the perpendicular (vertical) until you reach the point where *all* of the light is now being reflected back into the tub. The angle you are currently at when that occurs is the critical angle for that medium (water to air).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...


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QAId : 2431038
Asker : spucky
Subject : light speed relative to source speed
Private : No

Question : If you are driving in your car at precisely the speed of light and turn on your headlights, will anything happen? What if you were mph above and below light speed?

Answer : Rather than give myself CTS answering this myself (since it's a commonly-asked question) I'll just quote from the answer-king himself, Cecil Adams, author of the "Straight Dope") who has already done so:

http://www.straightdope.com/classics/a3_143.html

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 2431259
Asker : spucky
Subject : light speed relative to light source
Private : No

Question : "If you are driving in your car at precisely the speed of light and turn on your headlights, will anything happen?"
What about 1 mph slower and 1 mph faster?

Is light which is generated from a moving source affected speedwise by the speed/direction of the source? ie; The speed of the light coming from your headlights, (the light perpendicular to the lamps and in line with your trajectory) as you are driving at the speed of light, would it be twice the speed of light?

If I am stationary as you pass me in your car at the speed of light, and you tap your brakes 1 yard past me, (not enough to slow down) would I be able to see your brake-lights come on?

Answer : Rather than give myself CTS answering this myself (since it's a commonly-asked question) I'll just quote from the answer-king himself, Cecil Adams, author of the "Straight Dope") who has already done so:

http://www.straightdope.com/classics/a3_143.html

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities






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QAId : 2446133
Asker : Anonymous
Subject : Understanding Energy
Private : Yes

Question : Hello. I read an article in the Scientific American magazine about recent advances in teleportation by scanning a photon, destroying it, and recreating it at another terminal. It stated that unlike the Star Trek teleporter you need to send the information only, not energy.

As a matter of curiousity, if you convert a person into energy, will the individual die?

Note: I am 12 years old and I'm just beginning to understanding physics and quantum physics. If this question sounds a bit dumb I apologize. It's just that I hate not knowing or understanding something.

regards,

Anonymous

Answer : Well a photon and a person are quite different things. You can think of a photon as a "piece" of light, if you will. You probably already knew that but it's best not to assume anything. Light is a phenomenon similar to sound (that is, both consist of wavelength and frequency). Just as a sound can be recorded and played back (like on your CD player) it sounds as if they have found a way to take a similar snapshot of a light photon and transport (and regenerate) it elsewhere. Since light is energy already, there is no real transportation taking place, just the noting of frequency and wavelength of the light. To do the same with a person would involve far more complex processes since you'd have to be able to note the entirety of a human body's condition and makeup at a single point in time and then reassemble that "data" back into it's constituent components at the other end. As for whther they would die during this transition or not should at the time we talk about it be a moot issue as hopefully that kink would be out of a production system. ;-)

If this were feasible I imagine you could use this as a time machine of sorts. People who wanted to live in a future time, or that had incurable diseases that may be cured in the future could be "recorded" in this way and stored as data until the time they desired to be regenerated, presumably at which time they would be regenerated as they were recorded. Sounds like sci-fi to me...

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5

FUQuestion : Hello again!

I once saw a tv movie where a crew aboard a ship had a teleporting device that was capable of bending and folding the space around the people traveling in it intstead of converting them into energy. It is considered safe and reliable.

1)Is the warp teleporter more plausible in principle?

2)Do you have any ideas or theories on how it may be possible to teleport people without converting them into energy?

regards,

anonymous

Answer : I think this is based on the idea of a wormhole, where space is indeed curved and there is a shorter path to places than a straight line. We can't even use these to any effect now, so I really can't postulate on what uses for teleporting there might be...

As for #2 I'm still waiting for my air hovercar I was promised back in the 60s... ;-)

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 2464336
Asker : natashad_dig56
Subject : Electromagnetic Radiation
Private : No

Question : Hi I was wondering if you could help me find any answers to the following questions?...

1. Explain what is meant by 'wavelength'

2. (a) Which part of the visible spectrum had the shortest wavelength?

(b) Which part of the visible spectrum has the longest wavelength?

3. (a) The diameter of the Earth is approximately 12,500 km. Calculate the circumference of the Earth using the formula Circumference = Pi x Diameter ( Pi = 3.142 ).

(b) What is the speed of light?

(c) Knowing the circumference of the Earth and the speed of light, calculate how many times a ray of light would circumnavigate the Earth in one second - assuming it could!

4. (a) List at least five different applications of electromagnetic radiation (EMR) From the spectrum.

Thank you, and YES I will rate you on this.

My e-mail if it doesn't show up on the letter, my other contact is;
magenta_kinky@hotmail.com
thank you once again.

Answer : This looks a lot like homework questions, which I normally don't answer (that's your job, remember?) but in this case I'll make an exception.

1) Wavelength is simply one of the components of a wave phenomena - strictly defined it is the distance between identical portions of a wave (say crest to crest). All electromagnetic radiation (indeed all wave phenomena), regardless of wavelength, travels at the same speed. Since this is true, yet the wavelengths can be different, there must be another factor. IOW - one wavelength of ER may have a wavelength of .01mm and another may have a wavelength of 1/10-billionth of a mm and yet they both travel the same distance in the same time. The missing component here is how frequently the wave oscillates. This is called frequency and is a measure of how many waves per second are generated. A given wavelength of ER must therefore dictate a frequency which, when the two are mulitplied together, will equal the speed of light. So wavelength is inversely related to frequency. When wavelength is large, frequency is small, and vice-versa.

2) The shortest-wavelengths of visible light would in the blue/violet area. Per #1 above these wavelengths being the shortest would have correspondingly higher frequencies that the longer-wavelengths below. The longest-wavelengths (and correspondingly lowest frequencies) in the visible spectrum would be around deep red.

3a) Using your given diameter of 12,500 km:

radius (1/2 of diameter) is 6,250
Formula for circumference is 2 * pi * R
So...

6250 x 3.142 x 2 = 39275km

3b) Light travels around 300,000km a second

3c) So light would circle the Earth 7 1/2 times in one second.

300000km / 39725km

4a) Now this really *is* a homework question - you'd better not plagiarize - give attributions where needed. Which spectrum you mean is unclear - I'll assume you mean visible.

a - incandescent light bulbs
b - (neon and other) lights
c - lasers
d - flourescent bulbs
e - mercury vapor lamps that light streets
f - could almost inlcude tanning beds except they use ultraviolet - a bit out of our sense range

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities





Rating : 5


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QAId : 2501785
Asker : Bigal852
Subject : Gravity
Private : Yes

Question : When an object is dropped, it falls 32 ft the first second, 64 ft the next second, 128 ft the third second and so on. When a rifle bullit is
fired out of a barrel horizontaly at 3000 ft per
second, does it also fall 32 ft the first second???
A WW1 German gun would fire a projectile at 45
degrees elevation 75 miles shelling Paris. When
does the 32 ft per second come into play.
I am missing something to understand this action.
Please enlighten me. Thank you Bigal@sunet.net
Bigal852, 11749

Answer : You have a mistake there. In the first second of fall an object accelerates to a *speed* of 32 ft/sec, over which time it actually falls the average of it's speed at the beginning (0 ft/sec) and at the end (32 ft/sec) of that first second, or roughly 16 feet. The distance fallen is found by the formual

1/2*gt^2

where g is the gravitational constant (9.8m/sec or 32 ft/sec, whichever you like) and t is the time in seconds that the object has fallen.

The speed of an object after t seconds is simply:

gt

So, for example, an object falls for 4 seconds. It's speed at the end of that fall is:

32 * 4 = 128 ft/sec

and it's distance fallen is:

1/2 * 32 * 4^2

1/2 * 32 * 16

16 * 16 = 256 feet fallen in 4 seconds

Now as for your gun question... gravity does not take a holiday for moving objects. The second the projectile leaves the barrel it is subject to the same acceleration as any other object and "falls" (actually decelerates *downward*) at the same rate as discussed above. Picture separately the horizontal (from Germany to Paris) component of the object's motion from the vertical component (gravity) of it's motion and it will be clearer to you. The horizontal motion has nothing to do with gravity, and everything to do with the speed at which it is launched and the friction of the air through which it travels. If the projectile were to come to rest, horizontally-speaking, it would be due to the retarding force of the air on it. Of course this is not likely since, long before this complete slowdown can take place, gravity will have brought the projectile down to Earth (or the projectile will enter outer space if travelling fast enough, and will not be seen again if travelling faster still).

A good way to picture this is to imagine they fired the gun aimed directly parallel to the ground, towards a "level" landscape (no unexpected terrain modifications other than the normal Earth curvature). In this scenario the same rules apply. Let's say the gun is 16 feet off the ground when the projectile is fired. Gravity begins the downward acceleration as soon as the projectile leaves the muzzle - during the first second of travel the projectile traverses 3000 feet (per your 3000 ft/sec muzzle velocity). During that same second gravity has worked it's charms and brought the projectile 16 feet nearer the ground, at which point it strikes the ground (since the muzzle was 16 feet high when fired). This is what is happening to the long-range gun too (i.e. it falls the same 16 feet in the first second, but due to it's angle of 45 degrees gains significantly more altitude during the first second than is lost to gravity). By the time gravity has reduced this upwards trend (where distance vertically increased from projectile speed is less than the accelerated distance downwards by gravity) the projectile has travelled a long way up and, for a brief moment is vertically unmoving (when the upwards velocity and the downwards acceleration are equal). After this point we reverse and begin to build the downward side of our complete arc of travel, taking the same amount of time (minus air resistance which actually will retard the projectile's horizontal travel) to eventually land at our target.

With our same example gun pointing perfectly parallel to a ficticiously smooth Earth (also assuming no air resistance) you can increase the muzzle velocity higher and higher, with the result being that in that first second of freefall after leaving the gun you traverse longer horizontal distances. Where it gets interesting is when you get to a muzzle velocity of 8km/sec. At this speed *you will now traverse a horizontal distance equivalent to the amount of height loss due to the curvature of the earth*. In other words, every 8km the Earth's surface drops off 16 feet so this projectile can now be said to be in orbit around the Earth (better duck when it makes it back around to you)! In truth an object like this (our projectile or a satellite for instance) is "falling" around the Earth since it traverses a distance horizontally such that the vertical distance lost during that time due to gravity's acceleration is the same as the distance from the Earth's surface lost due to the Earth's curvature. The object is in equilibrium with gravity and will continue to be so unless another force impedes on it (in reality air resistance would be not allow this to continue, but you get the idea).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...

FUQuestion : Dear Paul,
In my stupidity I lost the URL to your answer to my question on gravity and the speeding bullet. I would
like to put it into my documents folder via the copy and paste method. Could you give it to me again.
Bigal@sunet.net Big Al 852, 11749
Thank you for your in depth answer. It is terrfic.

Answer : Sending it to you in email.... unfortunately you made it a private question so it's not visible in the normal view. Please use private questions for truly private topics. This was one I would have liked for all to see. Perhaps you could re-ask it and I can paste the same answer in?


You're very welcome - I'm glad you liked the answer...

Paul

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : When an objectis dropped,it falls 32 ft the first
second, 64 ft the next second, 128 ft the third
second and so on. When a rifle bullet is fired out of
a barrel horizontaly at 3000 ft per second, does it
also fall 32 ft the first second??? A WW1 German gun
would fire a projectile at 45 degree elevation 75
miles shelling Paris. When does the 32 ft per second
come into play? I am missing something to understand this action. Please enlighten me. Thank you.
Bigal 852, 11749

Answer : Thanks for the attempt but you'll need to create a whole new question, not just another added to this existing one, for others to see it.

Try again please...

Paul

FUQuestion : Dear Paul,
I have a match rifle with a very precision 30 caliber
bore,.308 in, that fires a projectile at 3000 feet
per second muzzel volicity within 1 minute of angle.
The target is 30 inches in diameter, 1000 yards
distant. The instant the projectile leaves the barrel
gravity starts to pull it down so that makes the path
of the bullet on it's way to the taget an arc. The
rifle has a telescopic sight with a micrometer
elevation adjustment. My question is what is the
formula that can be used to adjust the telescopic
sight necessary to hit the bullseye, windage being
neglegible. Thank you, Big Al 852
Rating : 5
Declined (Reason) : I'm not good enough with trig to give you a formula for the angle to fire at to arrive at the target, sorry. :-)


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QAId : 2547979
Asker : salt28
Subject : fusion
Private : No

Question : Hello smart people.
I would like to know how fusion works(H>>HE).

Answer : It's not just any old atom that can be "split" - and that's really a misnomer anyway as we don't do the splitting - the atom does so spontaneously under the right circumstances. Uranium is used for this purpose as it is a cumbersome atom being one of the most massive in terms of the number of nucleons present in it.


The nucleus, as you may or may not know, is composed of neutrons (negative charge) and protons (positive charge). When referring to a nucleus the protons and neutrons are collectively referred to as nucleons. A nucleon in isolation has a constant mass, or amount of material that makes it up. What is interesting is that this mass is *not* always a constant amount. What do I mean? Well for example, a hydrogen atom is the simplest element, consisting of a single proton in the nucleus and one electron in orbit. Let's say this proton has a mass of 'X'. In a hydrogen atom this is the maximum mass a proton can ever have. When more than one proton or neutron share a nucleus there is a strong nuclear force that bonds them together and that actually *reduces the mass of each element thus bonded.* If you were to measure the mass of a proton outside a nucleus you would find it at full mass. If you then measured it's mass inside a nucleus consisting of the proton and a neutron you would find some of the mass 'gone' in the form of the nuclear bonding force holding the two together. This is important to understand - I will now be using a term "mass-per-nucleon" which is an indication of the average retained mass (from it's normal full-mass state) of each element of the nucleus in different elements. It's a way to compare the loss of mass between differing elements (thus between differing atomic configurations). Once more than one nucleon is present in the nucleus the mass per nucleon starts to fall very quickly. The quickest change comes from hydrogen to helium since this is the very first introduction of a more mass-decreasing nucleons. As we move along the scale of atomic complexity (adding more protons and neutrons as we go) the mass-per-nucleon continues to drop as denser symmetrical nucleuses are formed. After one of the most stable and dense nucleuses, iron, however, something starts to happen. The atoms more complex (heavier) than iron start to reverse this trend, increasing in mass-per-nucleon. This is due to lack of symmetry in these denser atoms - some nucleons are not bound on as many sides as in the less-dense atoms thus increasing their mass (since the nuclear bonding force does not act as strongly when they are farther from neighboring nucleons - thus they lose less mass). When you get to an atom like uranium you have a highly unstable configuration which results in a high mass-per-nulceon. When uranium or plutonium absorbs a neutron they become unstable and electrical respulsion of the large number of protons overcomes the nuclear bonding force and the atom splits into fragments. The energy of a nuclear bomb or of a nuclear reactor comes from the fact that *the total mass-per-nucleon of the resulting fragments is less (since the fragments are more stable nucleuses and thus have more symmetrical layouts) than the mass-per-nucleon of the same number of protons and neutrons before the atom split* - this difference is the energy given off in kinetic (the fragments ejected during the splitting) and radioactive form.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : The above was pulled from an answer I gave previously on fission and nuclear energy in general. The same concepts apply to fusion only now you are coming from a very high mass-per-nucleon atom like hydrogen, and creating a new element with a *greatly* reduced mass-per-nucleon (relative to uranium/plutonium anyway) like helium. As in fission a small percentage of this lost mass-per-nucleon is given off as energy.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5

Answer : Quite right... I typod that one. Thanks for the sharp eyesight!




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QAId : 2553890
Asker : ruko
Subject : Speed of light
Private : No

Question : Speed of light question:

Lets say I have a powerfull light that can shine to the moon and I hook this light to a spinning shaft at say 2000 rpm. Each revelotion produces a beam of light that races across the surface of the moon. Lets say I have a method of measuring how long it takes for this beam to go from point A to point B on the moon surface.

If you calculate the velocity of the beam at the moon's distance, you will find that it is traveling much faster than the speed of light.

Is there something wrong with this since nothing can go faster than light?

Thank you

Ruko

Need More Information : What is it you think you're measuring that is surpassing the speed of light? You are measuring a linear distance that a light beam traces across the moon as evidence of faster-than-light interaction? I think all you're measuring is the difference between two light pulses (the photons emitted that struck at point A, and the ones that struck at point B) which were emitted, and travelled at, the speed of light. Interesting concept though...

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : I thought I was measuring the time it took for the spot of light to go from A to B which would be faster than light could travel that particular distance. Not being too hep on physics I suppose it is a rediculous question.

Thanks for your answer.

Ruko

Answer : It's actually quite an interesting proposal I thought...

Have you actually worked out the distance that wqould be covered at 2000RPM at the distance of the moon? It would be interesting to see what that worked out to be in terms of linear distaqnce across the moon's surface.

But you have to be clear that that distance is not being covered by the light itself, it's being caused by the rotattion of your light source, which I'll maintain, still has light leaving it constantly at velocity c. Do you see the difference between waving your flashlight at the wall vigorously back and forth and timing the light beam on the walll as it wiggles back and forth versus placing a light *on* the wall and measuring how long it took a beam of light to travel the same distance? In only the second are you measuring the speed of light. In the first you're measuring the the speed of the "wiggle".

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : Yes, I am attempting to measure the speed of the "wiggle" on the wall or the moon. You asked if I had calculated the speed of the beam at the moon's surface with a rotating light at 2000 rpm. It is over 50 million miles per second according to my calculations.

Thanks again.

Ruko

Answer : You're welcome...

Paul

Answer : Don't forget to rate the answers you receive on AskMe.com...

Rating : 5


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QAId : 2555562
Asker : mkritz
Subject : weight of the ocean...
Private : No

Question : why is it with all the millions of tons of water in the oceans that the bottom is not as hard as concrete.

Need More Information : That's a real good question. What makes you think it isn't (playing D's A here)? I'd expect it *is* harder than the same material (mud?) above water for the pressure factor you mentioned and for the fact that it's darn cold down there (4 degrees Celsius to be exact).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : i'm making this judgement from what i've seen on tv. i recall documentaries of the ocean floor, so deep there was no light of course. but the camera would show dust being kicked around.

Answer : Once a dust particle is liberated from the ocean floor the net effect on it individually is simply the *difference* between the pressure on all sides and that from above and below. Necessarily (since water pressure increases with depth) the water pressure from above will be (in this case very slightly) less than the pressure exerted from below. This is the essense of the concept of bouyancy. If the difference between the upward pressure and downward pressure is greater than the objects weight, the object will float up, eventually to the surface. If the difference is less it will sink. If the forces are equal (or very near) the object will simply hover and move neither up nor down.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 2573553
Asker : brood_009@...
Subject : Electromagnetic Spectrum
Private : No

Question : I know that visiable light only accounts for a small portions of a stars radiation, but what other regions of the electromagnetic spectrum are represented? Are any of these useful to astronomers? Any help would be great!

Answer : I think astronomers typically do not use visible frequencies for much real observing. Radio waves, X-Rays and other out-of-visible-band radiation are used. The higher frequency ones probably show more detail than visible light can due to their shorter wavelength.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 2574280
Asker : Anonymous
Subject : Physics
Private : No

Question : Hello. Could you please tell/describe to me HOW stellar line emission spectra are formed?

Answer : I believe you are referring to the technique whereby the make-up of interplanetary objects can be derived by examining the frequencies of electromagnetic radiation it gives off. If that is indeed your question this is the same concept behind the colors of light given off by neon signs. Each gas produces a different range of frequencies, giving each gas it's unique color (neon being red, argon being a light blue, and so on). These spectrum are the result of the finite possible electron orbit jumps available to a particular atom type (neon, argon, etc).

By examining the frequencies and patterns of ER that come from distant objects scientists can determine the makeup of the object.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 2575374
Asker : amit_mentch
Subject : cycling
Private : No

Question : Why doesn't my bike fall when I ride it ,but does when I just sit on it?

Answer : When a bicycle wheel is at rest it's simply a tall, skinny piece of mass that, if tilted even slightly, will fall due to the torque produced by gravity. When in motion, however, a bicycle wheel becomes more like a gyroscope. It's mass is mostly concentrated on the outer edge (main part of the wheel and tire are both present here) and this produces a relatively large rotational inertia. If you were to suspend a bicycle wheel in the air on chains (to each axle side) and spin the wheel, you would find it becomes difficult to rotate the tire away from a perpendicular while spinning. This stabilizing effect is what helps a bicycle stay upright when moving.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion :
how does it happen in objects that have very small wheels (like rollerblades) ,is your answer is valid
for such vehicles too?

Answer : They have rotational inertia also (and relative to their size, wider "tires" too) but the effect is much less. Have you ever skated on a single rollerblade? How did it compare to the stability of a bicycle? Probably not very well... :-)

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5
End :


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QAId : 2581145
Asker : Anonymous
Subject : Gravity
Private : No

Question : When an objectis dropped,it falls 32 ft the first
second, 64 ft the next second, 128 ft the third
second and so on. When a rifle bullet is fired out of
a barrel horizontaly at 3000 ft per second, does it
also fall 32 ft the first second??? A WW1 German gun
would fire a projectile at 45 degree elevation 75
miles shelling Paris. When does the 32 ft per second
come into play? I am missing something to understand this action. Please enlighten me. Thank you.

Answer : You have a mistake there. In the first second of fall an object accelerates to a *speed* of 32 ft/sec, over which time it actually falls the average of it's speed at the beginning (0 ft/sec) and at the end (32 ft/sec) of that first second, or roughly 16 feet. The distance fallen is found by the formual

1/2*gt^2

where g is the gravitational constant (9.8m/sec or 32 ft/sec, whichever you like) and t is the time in seconds that the object has fallen.

The speed of an object after t seconds is simply:

gt

So, for example, an object falls for 4 seconds. It's speed at the end of that fall is:

32 * 4 = 128 ft/sec

and it's distance fallen is:

1/2 * 32 * 4^2

1/2 * 32 * 16

16 * 16 = 256 feet fallen in 4 seconds

Now as for your gun question... gravity does not take a holiday for moving objects. The second the projectile leaves the barrel it is subject to the same acceleration as any other object and "falls" (actually decelerates *downward*) at the same rate as discussed above. Picture separately the horizontal (from Germany to Paris) component of the object's motion from the vertical component (gravity) of it's motion and it will be clearer to you. The horizontal motion has nothing to do with gravity, and everything to do with the speed at which it is launched and the friction of the air through which it travels. If the projectile were to come to rest, horizontally-speaking, it would be due to the retarding force of the air on it. Of course this is not likely since, long before this complete slowdown can take place, gravity will have brought the projectile down to Earth (or the projectile will enter outer space if travelling fast enough, and will not be seen again if travelling faster still).

A good way to picture this is to imagine they fired the gun aimed directly parallel to the ground, towards a "level" landscape (no unexpected terrain modifications other than the normal Earth curvature). In this scenario the same rules apply. Let's say the gun is 16 feet off the ground when the projectile is fired. Gravity begins the downward acceleration as soon as the projectile leaves the muzzle - during the first second of travel the projectile traverses 3000 feet (per your 3000 ft/sec muzzle velocity). During that same second gravity has worked it's charms and brought the projectile 16 feet nearer the ground, at which point it strikes the ground (since the muzzle was 16 feet high when fired). This is what is happening to the long-range gun too (i.e. it falls the same 16 feet in the first second, but due to it's angle of 45 degrees gains significantly more altitude during the first second than is lost to gravity). By the time gravity has reduced this upwards trend (where distance vertically increased from projectile speed is less than the accelerated distance downwards by gravity) the projectile has travelled a long way up and, for a brief moment is vertically unmoving (when the upwards velocity and the downwards acceleration are equal). After this point we reverse and begin to build the downward side of our complete arc of travel, taking the same amount of time (minus air resistance which actually will retard the projectile's horizontal travel) to eventually land at our target.

With our same example gun pointing perfectly parallel to a ficticiously smooth Earth (also assuming no air resistance) you can increase the muzzle velocity higher and higher, with the result being that in that first second of freefall after leaving the gun you traverse longer horizontal distances. Where it gets interesting is when you get to a muzzle velocity of 8km/sec. At this speed *you will now traverse a horizontal distance equivalent to the amount of height loss due to the curvature of the earth*. In other words, every 8km the Earth's surface drops off 16 feet so this projectile can now be said to be in orbit around the Earth (better duck when it makes it back around to you)! In truth an object like this (our projectile or a satellite for instance) is "falling" around the Earth since it traverses a distance horizontally such that the vertical distance lost during that time due to gravity's acceleration is the same as the distance from the Earth's surface lost due to the Earth's curvature. The object is in equilibrium with gravity and will continue to be so unless another force impedes on it (in reality air resistance would be not allow this to continue, but you get the idea).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 2635614
Asker : AstroConstant
Subject : Finding a good reference book
Private : No

Question : Hi,
I just want to ask you about a good reference book on physics.
I have taken physics as a subject in my studies but I didn’t find my syllabus book, good enough because there are some topics that I want to understand but I can’t find enough information about them in my syllabus book.
So, please help me.
You can also tell me about more than one book, I mean that if there are two or three books which all are considered to be the best reference books then tell me about all of them.
I will buy all.
Also, please consider that the reference book should cover all the fundamental concepts of all of the branches of physics.
Please give as much information as you can about the book i.e….

Name of author(s)
Title of Book
Name of publishers
Edition

Thanx…….

Answer : Here is the one and only book I recommend (and I highly recommend it!) for understanding physics concepts. Get it, and be glad... Paul Hewitt is a credit to the physics community...

http://www.amazon.com/exec/obidos/ASIN/0321009711/o/qid=967305528/sr=2-1/103-3896568-7255048

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 2661263
Asker : tjdusdl
Subject : first and second condition of equilibrium
Private : No

Question : how is force related to the distance from the fulcrum of a stick?(second condition of equilibrium)

How is angle and weight related to the tension?
(first condition of equilibrium)

Answer : Torque produced across a fulcrum is simply the downward force multiplied by the linear distance from the fulcrum. A see-saw is the best example. If you have two children, one weighing 50lbs and another weighing 100lbs for them to be in equilibrium the 100lb child's distance from his side of the fulcrum must be half that of the 50lb child's to produce equivalent torque.

As for angle (of the force/weight?). It may be that the angle of attack of the force (if severely away from the perpendicular) can either increase or decrease the torque, but primarily it is the force (weight) itself.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 3


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QAId : 2669188
Asker : priyaimports@...
Subject : physics,motion
Private : No

Question : dear respected sir ,

I AM A BIT WEAK IN PHYSICS SO I NEED YOUR HELP. WHAT IS MOTION ,POTENTIOLENERGY ,KINETICENERGY SAY WITH SIMPLE EXAMPLES .KINETICENERGYS FORMULA IS MVSQUAR.WHAT IS COLLUSION AND WHO THE MOMENTUM
BEFORE IMPACT =AFTER IMPACT

Answer : Motion is simply matter that is not at rest with regard to another object. Like a baseball thrown through the air.

Kinetic energy is energy of motion. The baseball has kinetic energy in it's motion as it moves across the sky. Kinetic energy becomes other forms of energy when the previously moving object stops. For example when the baseball strikes the ground part of it's kinetic energy becomes heat. A hammer striking a nail also makes the nail hot, as the hammer's kinetic energy is transferred as heat into the nail (and hammer).

Potential energy in this example would be exemplified by holding a baseball motionless above the ground. The baseball has potential energy due to it's elevation. If the baseball were to be released it would fall, and it's potential energy would be converted to kinetic energy as it falls until, by the time it reaches the ground, all the potential has been converted to kinetic (it's reached it's maximum speed just as it impacts the ground). A good way to think of potential energy is that it exists *because work was required to get the baseball to the height iwas at to begin with* and the energy used for that purpose is what we mean by potential energy.

Momentum is the product of mass and velocity. The more massive an object is, or the faster it travels, the more momentum it will have. Momentum is what makes things hard to stop. A slow baseball is easy to catch and doesn't hurt much. A fast baseball (same mass of course) hurts a lot. This is why a bullet is so dangerous - it has a lot smaller mass than a baseball but it's travelling much faster so it's momentum is great.

To determine final motion in an inelastic collision (where the objects don't deform on impact) you compare relative velocities (speed *and* direction of travel) and masses and you can then easily see the result. For example with two identical-shaped spheres - one of lead and another of aluminum (say the lead has a mass of 10 and the other a mass of 5). If we assume the objects are travelling the same speed and hit directly head-on into each other the result will be (minus a little lost momentum as heat from the collision) that the aluminum sphere will now have a negative direction of motion (backwards from where it came) at half the speed it held when it approached. The same result would happen if the spheres were the same mass (made of the material) and one was travelling twice as fast as the other.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5
Rating : 5


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QAId : 2670069
Asker : Viper3n
Subject : school
Private : No

Question : I'm about to take physics in highschool. Can u tell me what psychis is a bout and what sites can help me

Answer : Physics is one of the most practical sciences around. It is the basis for almost all other fields of science in that it is involved with the most basic principles that underly:

energy
matter

In physics you will open yourself up to concepts you are familiar with, but may never have though about (like why the sky is blue), and to concepts with which you operate on a daily basis but didn't really know how they worked (how light is generated by a light bulb for instance). Physics is a lot of fun and will open up your understanding of our world and in my opinion will grant you new respect for the symmetry and organization in the universe (IMO firm evidence of God).

I hope you enjoy physics as much as I do!

Sincerely,
Paul Doherty

A few web resources to get you started:

http://www.conceptualphysics.com
http://www.arborsci.com/Conphys.htm

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 2677367
Asker : rida_rules
Subject : specific heat capacity
Private : No

Question : supose that we are sitting in jamaica. there is a jaccuzi on our terrace and a few rocks beside it . both of them recieve the same amount of sunlight. when night falls which is a better way to keep the water in the jaccuzi warmer
a)leaving the water as it is in the jaccuzi
or
b)putting the sun-baked rocks inside the jaccuzi
explain

Answer : The answer depends on two things:

1) Which (the rock or the water) has a higher temperature upon the initial introduction of the rock to the water

2) Which has a higher specific heat - the water or the rocks?

I would suggest that water is one of the higher of known materials with regard to specific heat (that's why it's used in radiators in cars and hot water bottles).

For the unintitiated to the concept of specific heat it really comes down to a measurement of a material's resistance to a change in temperature. Water resists change highly thus it's specific heat is high. A great example of this is the beach where water and sand meet. During the day when the sun is out, barring any major weather patterns, the wind will blow in from the sea towards the beach. This is due to the sand heating quickly (low specific heat) in the sun, surpassing the temperature of the water (high specific heat) which is slower to warm. This produces convection currents in the air as the warmer air over the sand and land rises to be replaced by cooler air moving in from over the water in a circular fashion. But at night, once the sun goes down, specific heat again is shown as the rocks cool more quickly (remember specific heat is a resistance to *change* in temperature - this includes cooling as well as heating) than the water. The result is that the convection currents are reversed with the water retaining it's heat longer and creating convection currents that now move in the opposite direction (i.e. the wind now blows out towards the sea).

Now back to the rock/water question. I would suggest that *if* the rocks are hotter than the water I'd put them in, until their temperature was in equilibrium with the water (thus they gave up their additional heat to the water). Then I'd pull the buggers out of there. Not because of any further impact on temperature, but simply because who wants friggin rocks in their jacuzzi? :-)

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : The answer depends on two things:

1) Which (the rock or the water) has a higher temperature upon the initial introduction of the rock to the water

2) Which has a higher specific heat - the water or the rocks?

I would suggest that water is one of the higher of known materials with regard to specific heat (that's why it's used in radiators in cars and hot water bottles).

For the unintitiated to the concept of specific heat it really comes down to a measurement of a material's resistance to a change in temperature. Water resists change highly thus it's specific heat is high. A great example of this is the beach where water and sand meet. During the day when the sun is out, barring any major weather patterns, the wind will blow in from the sea towards the beach. This is due to the sand heating quickly (low specific heat) in the sun, surpassing the temperature of the water (high specific heat) which is slower to warm. This produces convection currents in the air as the warmer air over the sand and land rises to be replaced by cooler air moving in from over the water in a circular fashion. But at night, once the sun goes down, specific heat again is shown as the rocks cool more quickly (remember specific heat is a resistance to *change* in temperature - this includes cooling as well as heating) than the water. The result is that the convection currents are reversed with the water retaining it's heat longer and creating convection currents that now move in the opposite direction (i.e. the wind now blows out towards the sea).

Now back to the rock/water question. I would suggest that *if* the rocks are hotter than the water I'd put them in, until their temperature was in equilibrium with the water (thus they gave up their additional heat to the water). Then I'd pull the buggers out of there. Not because of any further impact on temperature, but simply because who wants friggin rocks in their jacuzzi? :-)

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : Whoops - hit the submit button twice.

Also in my sentence above:

But at night, once the sun goes down, specific heat again is shown as the rocks cool more quickly (remember specific heat is a resistance to *change* in temperature - this includes cooling as well as heating) than the water.

That reference to "rocks" should be "sand". Was thinking ahead to the rock question I guess... :-)

Answer : Don't forget to rate the answers you receive on AskMe.com...

End : This conversation is closed because the Expert has used it in a FAQ.


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QAId : 2692874
Asker : buffet02
Subject : quantum physics
Private : No

Question : Is it possible to synthesize excited bromide in an argon matrix? if so, how?

Thank you
Brian

Answer : Yes - but only if you use dry-ice slugs to obtain free coffee, and if you're prepared if gravity suddenly reversed itself! ;-)


--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : And of course you know that, if successful, that this procedure is like lazing a stick of dynamite and can be quite hazordous?

Be careful out there people!

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : Where is my spelling this morning? Hazardous...
Rating : 5