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Homework Help: Properties of Ocean waves

  1. Jan 5, 2010 #1
    1. The problem statement, all variables and given/known data

    A fisherman notices that his boat is moving up and down periodically, owing to waves on the surface of the water. It takes a time of 3.00 second for the boat to travel from its highest point to its lowest, a total distance of 0.690 meter . The fisherman sees that the wave crests are spaced a horizontal distance of 6.50 meter apart.

    What is the amplitude of each wave?

    2. Relevant equations

    3. The attempt at a solution

    If the maximum displacement is .690 wouldnt that be my amplitude of each wave, just need total understanding on this since, i read in my text its the total displacement of the crest and the total displacements of the trough.
    Last edited: Jan 5, 2010
  2. jcsd
  3. Jan 5, 2010 #2


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    Hi sphouxay, welcome to PF.

    Please include units in all of your statements, otherwise they are meaningless.

    The amplitude of a wave is indeed its maximum displacement from the equilibrium position in either direction. So, in this context, it is the height of a peak or the depth of a trough above or below the water's surface. Careful though. That is not quite the same as the "0.690" stated in the problem.

    Mathematically if a wave is described by A*sin(phase), then A is the amplitude, and the disturbance will oscillate between +A and -A.
  4. Jan 5, 2010 #3
    so are you saying the amplitude is 0.690/2, which is .345 meters
  5. Jan 5, 2010 #4


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    Yes, that is what I am saying.
  6. Jan 5, 2010 #5


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    Staff: Mentor

    Boat doesn't move just up and down, it rather makes circles or ellipses (depending on the water depth, I believe these are circles when the depth is large enough to be treated as infinite). So the total distance is half of the circle, which means amplitude is smaller.

    But I doubt question is that tricky.

    See http://en.wikipedia.org/wiki/File:Wave_motion-i18n-mod.svg
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