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Speed of a helicopter determined by sonar

  1. Sep 20, 2007 #1
    1. The problem statement, all variables and given/known data

    A helicopter flies directly toward a vertical cliff. when the helicopter is 700 m from the cliff face it transmits a sonar signal. it recives the reflected signal 3.4 s later. if the signal travels at a wind speed 350m/s, what is the speed of the helicopter.

    3. The attempt at a solution

    250*3.4= 1190 m
    plz help me what i need to do next? i spend 1 hour on it i did n't get answer.
     
  2. jcsd
  3. Sep 20, 2007 #2

    mgb_phys

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    How far did the signal travel in 3.4s?
    If the helicopter was stationary it would have to have travelled 2*700=1400m
    How much less did it travel?
    The helicopter must have travelled that far in 3.4s
     
  4. Sep 20, 2007 #3
    what u mean by 2*700?
     
  5. Sep 20, 2007 #4

    mgb_phys

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    The distance the sound would have to travel 700m to the cliff and 700m back to the helicopter = 1400m if the helicopter was stationary.
    In fact it only goes 3.4*350 = 1190m so the helicopter must have moved how much closer?
     
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