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Amazing thought worth a look

  1. Mar 31, 2008 #1
    according to the theory nothing is faster than light so if there were a rod very very long(eigth ligth min long) and then we were to pull it across with a velocity(applying either a force or impulse) then what will happen to the length of the rod?

    will it increase becoz the other end of the rod will start moving only after eigth minutes..........
     
    Last edited: Apr 1, 2008
  2. jcsd
  3. Apr 1, 2008 #2
    Yes. Relativity requires nothing is infinitely rigid (unstretchable).
     
  4. Apr 1, 2008 #3

    russ_watters

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    Impulses travel through a rod at the speed of sound in the rod.
     
  5. Apr 1, 2008 #4
    What if the rod were infinitely rigid?
     
  6. Apr 1, 2008 #5
    Relativity prohibits objects to be infinitely rigid (as already posted above).

    Read the thread completely next time.
     
  7. Apr 1, 2008 #6
    Of course. Sorry.
     
  8. Apr 1, 2008 #7
    yes nothing is rigid bt nothing is elastic to tht extent the rod is bound to break.........isnt it
     
  9. Apr 1, 2008 #8
    that was what i had in mind. but then it doesn't necessarily have to. it depends on the distance the rod is moved and the velocity of the displacement.
     
  10. Apr 1, 2008 #9
    Crazy question but I have to ask:

    What if instead of a rod you had a very long (eight light minutes long) billiards table and lined up the balls touching each other in a straight line with guides and struck the first ball with the cue ball. How long would it be until the ball at the other end jumped off?
     
  11. Apr 1, 2008 #10
    ur question is similar to mine and the answer to ur ques is the answer to mine

    "NOTHING IS PERFECTLY RIGID" and thus only after eigth minutes will the ball at the other end move..........
    crazy isnt it
     
  12. Apr 1, 2008 #11

    DaveC426913

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    It will take much, much longer than eight minutes, since the pulse will travel at the speed of the billiard balls, not the speed of light.

    Nice thread title, BTW. You in bulk marketing? :rolleyes:
     
  13. Apr 2, 2008 #12
    If the balls are touching they don't move. Mechanical pulses through "rigid" touching objects should travel at the same speed as mechanical pulses through a single "rigid" rod, although perhaps not at the speed of light. Mechanical pulses are not photons. I think mechanical pulse speed depends on the molecular structure of the "rigid" material. I wonder what the fastest mechanical pulse would be through? Perhaps a diamond? How fast would the pulse travel?
     
  14. Apr 2, 2008 #13

    bulk marketing why do u think that??
     
  15. Apr 2, 2008 #14
    Because your post sounds like spam.
     
  16. Apr 2, 2008 #15
    i dont get it dear and moreover i asked for an answer frm dave not u peter
     
  17. Apr 2, 2008 #16

    DaveC426913

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    Peter is my voice when I'm at other functions. His answer is bang on. (The only thing your thread title didn't do was promise I'll give my girlfriend a night she'll never forget.)
     
  18. Apr 2, 2008 #17

    DaveC426913

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    (Actually, the billiard balls will move because they are not perfectly rigid. The cue ball will compress one side, the wave of compression will pass through the ball and press on the next ball. In doing so, the centre of mass of the billiard ball will have moved a very small fraction.)

    Whether you bother to go into it in this detail or not, the point is that the shock wave will take much longer than 8 minutes - it will take as long as the speed of sound in the material that makes up the billiard balls, which will not be more than a few multiples of the speed of sound in air.
     
  19. Apr 2, 2008 #18
    hey zarbanx, just ignore ppl like dave. your question was interesting all right (if it really did come out of curiosity). i don't think they comprehend how physics or science for that matter really is done - it's not about remembering formulae but being curious.
     
  20. Apr 2, 2008 #19

    ZapperZ

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    OK, everyone, please stay on topic!

    Zz.
     
  21. Apr 2, 2008 #20

    russ_watters

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