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Apparent frequency of reflected wave

  1. Aug 3, 2014 #1
    1. The problem statement, all variables and given/known data

    A police car P with its siren on is chasing car T . The frequency of the siren is 1000hz. The speed of police car P is 30m/s . and the speed of car T is 40m/s . What's the apparent frequency of the siren heard by driver T > the ans is 967hz . I managed to get the ans for this.
    But i didnt managed to get the ans for part b .
    here's part b :
    What's the apparent frequency of the reflected wave heard by driver T ? the ans is 941 hz. p/s : i assume both P and T are moving to the right.

    2. Relevant equations



    3. The attempt at a solution
    apparent frequency of the siren heard by driver T = ((330-40)/(330-30))x 1000 = 967hz.

    b ) apparent frequency of the siren emitted by P to the left = (330/(330+30)) x 1000 = 917hz.

    apparent frequency of the siren reflected from the right and heard by T after reflection = ((330-40) / (330-30) ) x 917hz = 886hz . i am not sure which direction of the sound wave is reflected. can somoene explain on this?
     
  2. jcsd
  3. Aug 3, 2014 #2

    vela

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    Are you sure the question is asking about driver T hearing the reflected wave? It makes more sense that driver P hears the wave reflected off of T.
     
  4. Aug 3, 2014 #3
    yes the question asking T heard the wave
     
  5. Aug 3, 2014 #4

    HallsofIvy

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    Driver T can't hear the reflected wave- it is moving away from him.
     
  6. Aug 4, 2014 #5
    so is the question wrong?
     
  7. Aug 4, 2014 #6

    vela

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    Sounds like it. Try calculating the frequency P hears for the reflected wave.
     
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