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Homework Help: Wave Speed

  1. Nov 23, 2008 #1
    1. The problem statement, all variables and given/known data
    A person fishing from a pier observes that four crests pass by in 7.35 s and estimates the distance between two successive crests as 7 m. The timing starts with first crest and ends with fourth crest. What is the speed of the wave?


    2. Relevant equations
    f = 1/T
    v = f*d

    3. The attempt at a solution
    T = 7.35s/4 = 1.8375
    F = 1/T = 1/1.8375 = .544218
    V = .544218 * 7m = 3.81

    Can someone tell me what I'm doing wrong? Thanks!
     
  2. jcsd
  3. Nov 23, 2008 #2
    try using v=λ*f
     
  4. Nov 23, 2008 #3
    Thats what i did...
    V = .544218 * 7m

    isnt λ = .544218?
     
  5. Nov 23, 2008 #4
    oh right, well i got v=2.86 m/s
     
  6. Nov 23, 2008 #5
    The problem states the timing starts with the first and ends with the fourth wave.
     
  7. Nov 23, 2008 #6
    yeah precisely. you have to read the question carefully.
     
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