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Homework Help: Boat wavelength oscillation problem

  1. Feb 7, 2009 #1
    1. The problem statement, all variables and given/known data
    a father and son went on a cruise thats 20 ft long. the dad observed the cruise swayed thru 22 complete oscillations in 38 s, and one wave crest pass per/oscillation. the son noticed that each crest required 13s to reach land and the wavelenght is twice the length of the cruise. how far were they from land?

    2. Relevant equations
    velocity=wavelengh *f

    3. The attempt at a solution

    for the wavelenghth I have 13.33m because i converted ft into meters. then since they nentioned that the wavelenth is twice the size of the boat.
    I wanted to divide the number of complete ossiclation 22 by the 38s, but when it added that it takes 13 seconds for each crest to reach land. I got a little confused..
    should i continue to do that or should i figure how many crest had hiut land already??
    please help! thanks in advance.
    Last edited: Feb 7, 2009
  2. jcsd
  3. Feb 7, 2009 #2


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    Homework Helper

    Re: plz help asap!!

    How frequently were the wave lengths completing an oscillation?

    That gives you the T for 1 oscillation.

    Each wavelength is twice the length of the boat which is 20'.

    So that tells you the wave velocity doesn't it?

    Knowing the velocity and the time to shore, how far again is the shore?
  4. Feb 7, 2009 #3
    Re: plz help asap!!

    yes, that's what i was doing until they told me that it takes 13 second to shore. I didnt know where that time to shore belongs. So i did all that and my answer came to be 299.39m. is that correct?

    ThankYou LowlyPion. You have always been a great help and quick too.
    thank you thank you. I appreciate it
  5. Feb 7, 2009 #4


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    Re: plz help asap!!

    Once you have your wave speed, then surely you know that D = v*t

    Preserving more precision and noting that the dimensions used were kept in feet and not meters I get slightly more.

    13*40/(38/22) = ...
  6. Feb 7, 2009 #5
    Re: plz help asap!!

    yes, keeping in ft, i got 301 .. thank you so much for your help
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