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Homework Help: What is the frequency of the wave?

  1. Apr 18, 2015 #1
    A sound wave of the form s = sm cos(kx - ωt + φ) travels at 345 m/s through air in a long horizontal tube. At one instant, air molecule A at x = 2.00 m is at its maximum positive displacement of 6.30 nm and air molecule B at x = 2.09 m is at a positive displacement of 2.40 nm. All the molecules between A and B are at intermediate displacements. What is the frequency of the wave?

    Here is what ive gotten so far.
    s=6.30 nm at 2m
    s=240nm at 2.09
    since s is max at 2m, the sm=6.40nm

    kx-wt + phi=acos(s/sm)

    I have everything I need but, how do I find out what the value of a is?
  2. jcsd
  3. Apr 18, 2015 #2


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    There is no a, acos stands for arccos(y), the inverse cosine function.
  4. Apr 19, 2015 #3
    Thank you!
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