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How high is the wave crest?

You are in the water with your head just above the water line. The waves have amplitudes of 3 meters, wavelengths of 10 m, and speeds of 30 m. How high above your chin is the wave crest when you are in the deepest part of the trough? How long before you are in a deep trough again? Please explain, thank you

Update:

@Steve4physics - yeah but doesn't it say how high above your chin? So then how could it be 6 m if above your chin is 3 m?

Update 2:

@Steve4physics - here is what I was originally thinking, but correct me if I'm wrong. this is the way I was looking at things, so I figured above the chin is 3.0 m?

http://i.imgur.com/2Ovzxvs.jpg

1 Answer

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  • 7 years ago
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    EDITED as the diagram in the link I originally gave was not very good.

    __________________________________

    I guess you mean speed is 30m/s.

    From the bottom of a trough to the top of a crest is a height difference of twice the amplitude. So the answer is 2x3m = 6m

    Look at the diagram in the link and this should be clear.

    speed = distance/time, so time = distance/speed.

    When the wave travels exactly one full wavelength, you will be back in the next trough. This take a time T:

    T = distance/speed

    = wavelength/speed

    = 10/30

    = 0.33s

    (Check you have the question correct as 30m/s is a bit fast!)

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