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Can anyone explain or correct this?

  1. Oct 28, 2012 #1
  2. jcsd
  3. Oct 28, 2012 #2

    mfb

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    I think there would be other ways to fix energy conservation and you have to be more careful with the Doppler effect (needs an integration over the solid angle), but the basic idea is fine: The kinetic energy of the cat somehow depends on the energy content of the cat. Otherwise, "radiating+getting speed afterwards" would need the same energy as "getting speed + radiating" - but the light energy would be different.
     
  4. Oct 28, 2012 #3
    Thank you, but is that guy correct in calculating the Doppler energy gain to be (1+v^2/2c^2) not (1-v^2/2c^2)?
    Also he is using classical kinetic energy to derive the formula, is that appropriate?
     
  5. Oct 28, 2012 #4

    mfb

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    That is a bit sloppy, he should integrate over all emitted photons / space directions.

    That is another problem - you can derive that the classical formula does not work, but it is problematic to derive a new formula, based on the (wrong) old one. The result happens to fit, but that could be just by chance.
     
  6. Oct 28, 2012 #5
    I see, thank you very much for you help.
     
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