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Special relativity - observing spinning objects

  1. Oct 2, 2007 #1

    Mentz114

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    I did a thought experiment - suppose we have a simple clock comprising a disc rotating with constant angular velocity. We can read off time inervals by counting the revs.

    Another observer, passing at constant velocity will see the disc rotating at a slower rate, since moving clocks run slower.

    Does this mean that all spinning objects appear to be spinning slower from another frame ?

    In other words, does angular velocity transform like time in SR ?
     
    Last edited: Oct 2, 2007
  2. jcsd
  3. Oct 2, 2007 #2
    Yes, I think your observation is correct.

    Eugene.
     
  4. Oct 2, 2007 #3

    Mentz114

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    Hi Eugene,
    yes, it seems inevitable. It is a bit puzzling because angular velocity has dimension of reciprocal time.

    I wonder if angular momentum transforms the same ?

    M
     
    Last edited: Oct 3, 2007
  5. Oct 2, 2007 #4
    To be more precise, I think that the rotation period of a moving object should increase by the factor [itex] \gamma = (1-v^2/c^2)^{-1/2}[/itex]. Then the rotation speed of such an object should go down, i.e., the factor is [itex] \gamma^{-1} [/itex].

    Eugene.
     
  6. Oct 3, 2007 #5

    Mentz114

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    Agreed. Nothing to it. It's only a kinematic effect in any case. Thanks for the input.
     
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