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Doppler effect

  1. Jun 24, 2012 #1
    1. The problem statement, all variables and given/known data
    Man travels down the highway in his car whistling middle C
    A policeman has a defective radar gun but passed a physics course. He hears the
    pitch change from D(294 Hz) immediately above middle C(262Hz) to A#(233Hz) immediately below
    middle C as the car passes.
    a) How fast is Professor Zoom traveling?
    b) Should Professor Zoom get a ticket? if speed limit is 100km/hr


    2. Relevant equations
    f = frequency of source
    f1 = frequency at observer
    c = speed of sound (330m/s)
    v = velocity of observer
    v1 = velocity of source

    source moving towards stationary observer.
    f x c/(c-v1) = f1

    source moving away from stationary observer.
    f x c/(c + v1) = f1

    3. The attempt at a solution
    So for source moving towards stationary observer

    f x c/(c-v1) = f1

    262(330)/330-v1=294
    v1=36m/s

    source moving away from stationary observer.
    f x c/(c + v1) = f1

    262(330)/330+v1=233
    v1=41m/s

    I just want to know if im on the right track, or what am I doing wrong? and do i add those two velocity together? when you convert those velocities into km/h they surpass 100km/hr so I said that yes he does get a ticket. Help please :) im a little lost...
     
  2. jcsd
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