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Homework Help: Doppler effect problem

  1. May 7, 2009 #1
    1. The problem statement, all variables and given/known data

    Standing in line next to the scariest rollercoaster of all time, you see your friends screaming their heads off as they come speeding out of the end of the ride. The sound of their screams is about 30% higher in pitch than normal due to the Doppler shift caused by their motion towards you. If they sound normal again by the time the rollercoaster has halted about 1.5 seconds later, estimate how far the rollercoaster moved as it was coming to rest.

    2. Relevant equations

    f(observed)= f(emitted)((v(sound) +/- v(observer)/(v(sound) +/- v(source))

    3. The attempt at a solution

    My hunch on this problem is that I need to create some sort of ratio with the 30% given in the problem in order to solve it, and I know I'll have to do some algebra to get a velocity for my final answer. Would anyone be willing to brainstorm this with me? I'd really appreciate it!
  2. jcsd
  3. May 7, 2009 #2


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    Staff Emeritus
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    Homework Helper

    Yes, you'll need to use this equation to find v(source). Some other information to use:

    What is v(observer)?
    What's another relation between f(observed) and f(emitted), using the information given in the problem statement?
  4. May 9, 2009 #3
    Thank you for the help. I ended up figuring it out!
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