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Answer me this...


Hills Bro
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Hills Bro,

Did you know that Einstein had a very similar question to your thread starter when he was a boy?

Pondering it eventually led him to Relativity.

***

Belle,

Your question is interesting.

If the incline is frictionless the ball will slide, assuming no initial rotation is imparted.

If there is air present, then from the sliding ball's frame of reference the wind blowing past it's top will be greater than the wind blowing past it's bottom due to the incline setting up a little air blockage near the point where the ball touches the incline. As the ball picks up speed this wind differential will cause the ball to rotate a little bit BACKWARDS from a normal roll, the incline offering no resistance. It will look like it's trying to roll uphill as it slides downhill.

I'm assuming that the ball's surface has friction with the air, but it has no friction with the incline.

Edited by Mike
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I agree with you Brother Speed. I believe the ball will roll while sliding. However, one would expect it to roll in the directiion of the low part of the incline, I suggest that it will slide down the incline, but the friction from the atmosphere would cause the ball to rotate around an axis at it's center - not at it's top or bottom.

It will actually appear to spin around this axis while it slides down the incline. Furthermore the rate of spin and slide will both increase as the ball gets closer to the lower end of the incline.

of course there is another possibility!

IF the ball is the correct size to do so, and IF the incline is steep enough, the ball may not continue to move. Once is starts sliding, the force of the air at it's greatest girth may be large enough to overcome the gravitational force and hold the ball steady.

IF the force of the air moving across the ball is strong enough, the ball my be forced to slide uphill.

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krysilis,

It looks like the first part of your post is identical to my post.

You bring up an interesting possibility in the second part of your post: that a rapidly rotating ball may stop.

I will have to ponder that one. First guess is that this stopping mechanism will end as energy is disapated into the air, heating it up and ending the rotation.

The last line of your post is a definite no-no. The law of the conservation of energy dictates it will can never move upwards.

Edited by Mike
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krysilis,

It looks like the first part of your post is identical to my post.

You bring up an interesting possibility in the second part of your post: that a rapidly rotating ball may stop.

I will have to ponder that one. First guess is that this stopping mechanism will end as energy is disapated into the air, heating it up and ending the rotation.

The last line of your post is a definite no-no. The law of the conservation of energy dictates it will can never move upwards.

I don't think so Mike. In your scenario the ball would rotate around a perpendicular axis, in mine it would be a horizontal axis (with respect to the incline)

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I would like to go back to the light speed car question and challenge Brother Speed's theory. Granted I am not edumacated formally in this and your name does have "speed" in it this may be a foolish idea.

I think what might happen is that you see nothing but light or a lot more light than you would normally, at least in front of you. What in space is dark? Dark matter maybe? You can measure the darkest of points in space and measure its light energy and get the same curve as you would measuring a light sourse. In the darkest of space there is still light coming from every direction. We don't see light in all of space because the speed of light isn't fast enough. There are light sourses we can't reach because they are beyond our viewing capability or because the light has not reached us yet. It is too far away for us to see.

So unless we are traveling outside of our universe in an existence without light or inpenatrable to light (since we are in a "futruristic SPACE car" I would say we are not), I would think that we should still see light just perhaps different light (light that we couldn't see because of our distance and slow speed) or more light. Light does not travel in a sigular linear direction unless reflected and directed that way. So while the light may not reflect back to you, it will still be on. While you won't see the light that is coming from behind you I would think that you still see light that is coming towards you in the opposite direction perhaps to a greater degree. So perhaps you would be traveling into pure light with pure darkness behind you. Perhaps though you could see all the photons around you that are traveling at the same speed, billions of them. You would see the light reflecting from those particles because you are only moving in a singular direction in space.

Secondly I would say to Mr. Ham, that taveling the speed of light does not make you light anymore than traveling at the speed of sound makes you sound. What happens when you break the sound barrier?

BOOM!

So what happens when you break the light barrier? No light or more light? Both?

Perhaps you would need to turn on your "darks" to see where you are going.

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If your in your futuristic space car at midnight on a very dark night traveling at the speed of light and you turn off your headlights...what will happen? B) B) :unsure: :blink: <_<

Nothing unusual happens, the lights go off. At least if you are less than the speed of light, everything seems normal. You would supposedly acquire infinite mass AT the speed of light, though I'm not sure that MAKES you light. But relativity says the speed of light is the same for all reference points. So AT the speed of light the lights go off, but time stands still. LOL It means you have infinite mass and there is no time ... you are God :)

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... but the friction from the atmosphere would cause the ball to rotate around an axis at it's center - not at it's top or bottom.

It will actually appear to spin around this axis while it slides down the incline. Furthermore the rate of spin and slide will both increase as the ball gets closer to the lower end of the incline.

hmmmm, not at top or bottom, I assume the axis you speak of is parallel to the plane and perpendicular to the slope, in other words, just like it was rolling down WITH friction. I don't DO aerodynamics or fluid mechanics, but without the plane, it seems the air would act equally and cause no spin. The plane would maybe compress air underneath, possibly reducing air pressure under (perpendicular to the plane) the ball but since it is a ball, not a wing, I don't know if there is a net change. I'd guess not.

so maybe the speed it achieves down the slopes is the same as the speed it achieves in freefall.

of course there is another possibility!

IF the ball is the correct size to do so, and IF the incline is steep enough, the ball may not continue to move. Once is starts sliding, the force of the air at it's greatest girth may be large enough to overcome the gravitational force and hold the ball steady.

IF the force of the air moving across the ball is strong enough, the ball my be forced to slide uphill.

Now either I'm missing something here, or you need to be aware that the MJ they sell now is a LOT stronger than in the 70's. :D But really, how can the ball move uphill, unless it has a paraglider attached and a nice updraft?

I'll wait for a certified ME to show up with the correct answers for this and the relativity thingy. I like the thread though.

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If you would imagine a stream of water from a hose, I'm sure you could see that there could be enough pressure there to force the ball up hill. If enough draft of air existed, why would it not do the same thing?

And no, I expected the ball to spin on an axis as if the axis was E and W on its circumference, not N and S at the poles.

I have no problem if you don't like how I think. But the MJ comment was way out of line. ;) <_<

Edited by krysilis
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The paradox with the headlights was resolved by Einstein thusly: it is a physically impossible scenario to begin with as it is stated by Hills Bro.

A very similar and physically possible situation might be substituted for the thread starter thusly:

Q: If your in your futuristic space car at midnight on a very dark night traveling at 99.9999% the speed of light (relative to the earth) and you turn off your headlights...what will happen?

A: Nothing different than if you were traveling at 65 mph in a normal car on a freeway. What you would see your high beams do would be identical at any speed. There would be no measurable difference at all. This is the fundamental principle of Special Relativity.

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Since we are talking relativitity and the effect is relative to your frame of reference (from the deivers seat)

the effect would be indistinguashable and the same as if you were standing still. It is an impossible sceanaro but it would remain true for any speed up to (or faster than also?) the speed of light.

Edited by ckeer
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If you would imagine a stream of water from a hose, I'm sure you could see that there could be enough pressure there to force the ball up hill. If enough draft of air existed, why would it not do the same thing?

And no, I expected the ball to spin on an axis as if the axis was E and W on its circumference, not N and S at the poles.

I have no problem if you don't like how I think. But the MJ comment was way out of line. ;) <_<

:P no, I was not the least bit serious, I do like the way you think ... it was just light hearted banter, at least I laughed. :) I guess by the wink you are kidding? Anyway, it was just having fun, OK?

I mean of course if there was enough air blowing it would go uphill, but why would we introduce that into the equation?

I need to see why there would be spin ... maybe I need less wine ?

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Ok..take your average household fan and point it upward. If you take a balloon ..inflate it. set it in front of said fan.. it would stay suspended within the apex of the current flow..would it not? <_< :blink: :rolleyes: :huh:

Well ...what if I were to stand directly above said fan and pass gas. Would that gas remain in the same suspended state within the apex.. thus allowing me to take a bic lighter or even a personalized zippo..light it and see it explode? I think not. :unsure: :o :blink: But boy.. wouldn't that be fun. :lol:

Edited by Hills Bro
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Be careful lighting those farts!

There is a serious danger in lighting farts because there is a natural sucking reflex when you light your fart and some people actually suck it in and singe their private parts. If there's still gas in your intestines, it will all ignite and if your pants are down there could be some serious bodily hair damage.....especiallly if one is extremely hairy.

Yeah, I hung around some really fun guys in college. :blink: :wacko: :o

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First thing Belle I don't want to know anything about any sucking reflex mentioned in the same sentance the word fart is used in.

OK as far as the headlight goes. We must assume that the headlight is burning creating photons. Since they are traveling at the speed of light they are simpply building up in front of the car until it slows down. At that moment a HUGH flash of light will come from the front of the car.

As far as the ball rolling or sliding down a frictionless plane it is all relative to the smoothness of both the ball and the plane it is on. The moment it hits/stikes a bump it will start rolling. The specific gravity of the material of the ball will also come into place because it take energy to get the ball rolling. Gravity will just simply pull downward. A ball made of lead will start rolling at a slower pace than a ball made of plastic and filled with air.

Yes I know I have a way with this stuff. Wht else would I have taken all those physics classes in collage.

BE HAPPY this was not a disscussion on thermodynamics.

NOW IF I HAD ONLY LEARNED HOW TO SPELL.

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Thanks ex70's. Sorry for the previous post, but I don't want anyone trying any dangerous experiments on here. ;)

The only reason I passed physics was thanks to this really shy, really cute guy with a pocket protector, thick glasses and a homemade bowl cut. I taught him some things....he taught me some things. :wub: It was a win-win situation.

Edited by Belle
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How did travelling at the speed of light become lighting farts? Honestly, you people!

Sorry Ex70's, I disagree with the light burst from the headlight. Light travels at the speed of light which is a constant. You cannot simply push it to go faster. However, I did not know about the lead ball vs. a plastic filled with air ball.

Belle, you had fun with a nerd? Kewl, my wife does too. ;)

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