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Homework Help: Doppler Shift question

  1. Apr 18, 2004 #1
    A train moving toward a detector at 31m/s blows a 305-Hz horn. What frequency is detected by a statiory train?

    Using the equation f´= f(V + Vd/ V - Vs)

    The answer is supposed to be 340-Hz but I don't understand how to get it. Mind helping me out?
  2. jcsd
  3. Apr 18, 2004 #2
    anyone know?
  4. Apr 18, 2004 #3
    I do not recognize the formula. My scientific encyclopedia gives this for the source approaching the detector:

    [tex] f' = f(\frac{1}{1-\frac{v}{v_s}})[/tex]

    where v_s is the speed of sound in air.
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