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Energy and Momentum in Waves

  1. Oct 9, 2014 #1
    Suppose you have this energy density A*cos^2(wt-kx+delta)

    If you want find the velocity of this, I would suppose you would utilize the kinetic energy ?

    What is the formula in this case?
  2. jcsd
  3. Oct 9, 2014 #2


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    Since that energy density has ##k## and ##\omega## in it, I presume you know those parameters. In such a case, you can find the group and phase velocities in the following manner (I'm guessing this is a 1-D problem due to lack of vector symbols in your post):

    $$v_{gr}=\frac{\partial \omega}{\partial k}$$
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