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Homework Help: Determine the speed of the medium in transverse and longitudinal waves.

  1. Dec 6, 2009 #1
    1. The problem statement, all variables and given/known data
    In the situations where a transverse or longitudinal wave is propagating through a medium, the medium moves. How do you determine the speed of the medium's motion? When is the medium's speed at a maximum?

    2. Relevant equations
    The speed of the propagating wave is v = frequency X wavelength.
    speed of the medium = distance / time elapsed

    3. The attempt at a solution
    The speed at the maximum and minimum height from the wave's equilibrium point is 0.
    I think the speed of the medium during each oscillation due to the wave's propagation is greatest at the wave's equilibrium point. But does the medium accelerate when it ascends and descends from crest to trough, respectively? Is it necessary to find the length of the wave?
  2. jcsd
  3. Dec 6, 2009 #2


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    Think of a point of the medium as a point mass at the end of the spring. The instantaneous acceleration is zero at the equilibrium point in which case the speed is maximum whether it ascends or descends. You are correct,

    Your statement, speed of medium = distance / time elapsed is incorrect. It is correct only when the medium covers equal distances in equal times. This is not the case here. The velocity of the medium is v = dy/dt where y is the displacement of the medium from the equilibrium position. I suspect you are confusing the speed of the medium with the propagation velocity of the wave. They are different quantities.

    It is not necessary to find the wavelength.
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