Naked Science Forum
General Science => General Science => Topic started by: ken222nek on 31/03/2009 03:52:46
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We are told that nothing can travel faster than light, Now imagine I have a pool cue on the floor with a pool ball on floor in front of the cue, if i pushed the cue forward with my finger the cue would move forward and hit the ball so the energy from my finger was transferred through the cue into the ball.
Now imagine that pool cue was 2 billion miles long and again I pushed it forward with my finger and just as it did with the small cue it hits the ball, but if that was the case don`t it mean that the energy from my finger traveled along the 2 billion mile long cue in exactly the same amount of time it took to travel through the small cue as when I push one end the other end moves instantly, meaning the energy from my finger traveled faster than the speed of light.
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Not so. We had this topic on here a while ago but I can't find it. (OK I admit it. I'm too lazy to look [:P] )
Basically, the force is not transferred along the cue instantaneously. It travels at the speed of sound. The method of propogation is the same as that of sound, i.e. transference from 1 molecule to the next. I'm not sure what that speed would be in a wooden pool cue.
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Maybe this is what you were looking for Dr B
http://www.thenakedscientists.com/forum/index.php?topic=19164.0
The answer to this thread is about 4 posts down.
Cheers
justaskin
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justaskin - thanks. It actually starts at the 6th post down but we won't quibble [;)]
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I'm not sure what that speed would be in a wooden pool cue.
Around 4000 m/s:
http://hypertextbook.com/physics/waves/sound/
In case you want to measure it yourself:
http://www.instructables.com/id/How-to-measure-the-speed-of-sound-with-two-lumps-o/