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Third harmonic frequency

  1. Sep 24, 2015 #1
    1. The problem statement, all variables and given/known data
    A metal wire is vibrating at its third-harmonic frequency. 0.32 m from one end, the amplitude is equal to one quarter the maximum amplitude. Find the length of the wire.

    2. Relevant equations


    3. The attempt at a solution
    I don't quite understand the question, it says 0.32m from one end, is that from the start to the first node?

    the amplitude going to be 1/4 its maximum where sin(x) = 0.25, correct?
     
  2. jcsd
  3. Sep 24, 2015 #2

    haruspex

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    It is not clear to me whether the wire is fixed at either or both ends. I'd guess it's fixed at both. If so, the 'start' is a node, and .32m is the distance from there to the given point.
    It depends what you mean by x.
     
  4. Sep 24, 2015 #3
    if it helps, the hint the question has is : "The third harmonic will have a wavelength equal to 2/3 of the length of the string. Also, *note to self* the max-amplitude of this wave is (2A) not (A)."
     
  5. Sep 24, 2015 #4

    haruspex

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    So what does that tell you about whether one or both ends of the string are nodes?
     
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