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Homework Help: Doppler effect of a motorcycle

  1. Apr 6, 2006 #1
    a motorcycle starts from rest and accelerates along a straight line at 2.81m/s^2. the speed of sound is 343 m/s. a siren at the starting point remains stationary. how far has the motorcycle gone when the drive hears the frequency of the siren at 90.0% of the value it has when the motorcycle is stationry?

    sorry...i really do not understand this chapter and have no clue how to solve it, and i don't know where to begin..any help/clues would be appreciated. thanks
    Last edited: Apr 6, 2006
  2. jcsd
  3. Apr 6, 2006 #2
    A useful relationship is:
    speed of sound = wavelenth*frequency.
    If your moving away from the source, the frequcy will go down (the time between peaks goes up). So if your moving away and take a look at the soundwave comin' at you it seems slower.
  4. Apr 6, 2006 #3


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    Homework Helper

    The classical Doppler effect (that's all you have to worry about at this stage) has got two formulations, one for a moving observer and another for a moving source. First you have to decide which this is.

    Then quote the formula for the apparent frequency in terms of the real frequency, and we'll go from there. All this should be in your textbook, if not, here's a reference : http://www.sasked.gov.sk.ca/docs/physics/u5c32phy.html [Broken]
    Last edited by a moderator: May 2, 2017
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