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Wave Speed

  1. Mar 9, 2007 #1

    tdk

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    1. The problem statement, all variables and given/known data
    A group of swimmers is resting in the sun on an off shore raft. They estimate that 2.2 m seperates a trough from an adjacent crest of surface waves on a lake. They count 18 crests that pass by the raft in 31s. How fast are the waves moving?


    2. Relevant equations

    F= 1/t v=wavelength x frequency

    3. The attempt at a solution

    2.2(2)=4.4= wavelength

    4.4 x 31? or 4.4 x 18? or something else?
     
    Last edited by a moderator: Mar 9, 2007
  2. jcsd
  3. Mar 9, 2007 #2

    Dick

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    I think pugfug was being alarmist about the link. Welcome back. Sorry about the panic. Anyway we now want frequency, the number of wavelengths per second. How many wavelengths in 31 secs?
     
    Last edited: Mar 9, 2007
  4. Mar 9, 2007 #3

    Mentz114

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    You need to calculate how many crests pass per second, then multiply by wavelength. This gives distance/time which is a velocity.
     
  5. Mar 9, 2007 #4

    Astronuc

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    Correct. The wavelength is twice the peak-to-trough distance.

    Now speed is length/time, so find the total length of the waves passing the raft in t=31s.
     
  6. Mar 9, 2007 #5

    tdk

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    Ok so would I do 4.4 x 31? Or do I have to incorporate the 18 in there somewhere?
     
    Last edited by a moderator: Mar 9, 2007
  7. Mar 9, 2007 #6

    tdk

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    Sorry guys I know Im like kinda slow at this, I just suck really bad at physics and math in general really
     
    Last edited by a moderator: Mar 9, 2007
  8. Mar 9, 2007 #7

    Moonbear

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    tdk, I've been trying to get your attention privately, but am going to have to interrupt here publicly. I can't keep deleting that link for you. Your computer must be infected with a virus and I really don't want someone else inadvertently being infected with it through our site. Please run a virus/adware/spyware scan ASAP and clean up your computer.

    Folks, do NOT click on that link no matter how tempted. It apparently contains a virus.
     
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