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Homework Help: Doppler Effect Question

  1. May 12, 2006 #1
    For this problem, I used the Doppler Effect equation, and got 419.361 as my answer. I used + on the top and - on the bottom. Do I need to switch the two?
  2. jcsd
  3. May 12, 2006 #2

    Chi Meson

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    Since the suspect is going in the direction that is away from the sound source, you use a negative value for the observer speed. The source is moving in the direction toward the observer, so there is a positive source speed. That means you get (using the equation correctly):
    f_observed = f*[v+(-vo)]/[v-(+vs)]

    so there ends up being a - on both top and bottom. Did you follow that?
  4. May 12, 2006 #3
    Thanks, so the answer comes out to be 404.531 Hz?
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