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Periodic Waves

  1. Jan 13, 2008 #1
    1. The problem statement, all variables and given/known data

    A jetskier is moving at 9.8 m/s in the direction in which the waves on a lake are moving. Each time he passes over a crest, he feels a bump. The bumping frequency is 1.1 Hz, and the crests are separated by 5.6 m. What is the wave speed?



    2. Relevant equations

    velocity = frequency * wavelength

    3. The attempt at a solution

    I thought to multiply the 1.1 Hz which is the frequency by the 5.6 which is the wavelength to get a velocity...I got 6.16 m/s then I was not sure what to do next...should I add it to the jetskier's velocity 9.8 m/s because they are going in the same direction? What should I do?
     
  2. jcsd
  3. Jan 13, 2008 #2

    Kurdt

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    This is the doppler effect. For an observer moving away from the source of the waves (i.e. moving the the same direction) then the observed frequency is:

    [tex]f'=\left( 1-\frac{v_o}{v}\right) f [/tex]
     
  4. Jan 13, 2008 #3
    only the bumping frequency is given...how do I solve for the other frequency to plug into the equation
     
  5. Jan 14, 2008 #4

    Kurdt

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    Remember that frequency is the wave speed divided by the wavelength.
     
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