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Frequency Question

  1. Nov 19, 2009 #1
    1. The problem statement, all variables and given/known data
    A source of sound waves of frequency 1.0 kHz is traveling through the air at 0.50 times the speed of sound. (a) Find the frequency of the sound received by a stationary observer if the source moves towards her. (b) Repeat if the source moves away from her instead.

    2. Relevant equations

    F01 = fs/1-(vs/v)

    F02 = fs/1+(vs/v)

    3. The attempt at a solution
    I tried plugging in the values that are given to me, but I simply don't obtain the correct results. Please help? Thanks in advance.
  2. jcsd
  3. Nov 19, 2009 #2


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    Show your calculations.
  4. Nov 19, 2009 #3
    F01 = fs/1-(vs/v)

    F02 = fs/1+(vs/v)

    Using these equations, I plugged in:

    1/1+(343/171.5) = 3

    1/1-(343/171.5) = -1

    I'm not sure if I must do something regarding the 1kHz given to me, but neither of both numbers are valid answers.
  5. Nov 19, 2009 #4


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    Fs' = Fs/(1 - Vs/V)
    Fs = 1kHz, Vs = 171.5 m/s and V = 343 m/s.
    Now try.
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