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Homework Help: Find difference in echo times, doppler shift?

  1. Nov 19, 2011 #1
    1. The problem statement, all variables and given/known data
    A bat is pursuing an insect, and using echolocation of 41 kHz sound waves to track the insect. The insect is initially 34 cm from the bat but then moves to a distance of 44 cm as it tries to escape. What is the difference in the two echo times that the bat measures?

    2. Relevant equations
    I'm not sure... is this a doppler shift question? the book has a few sentences about bats using reflection time and doppler effect to judge distances of objects.

    This is an equation for radar: Ltot=vΔt

    Doppler shift (moving away from observer)

    3. The attempt at a solution
    I attempted to find time by using the Ltot=vΔt equation. 2(.34)=343t -> t=.0019s
    2(.44)=343t -> t=.0026s. Obviously wrong. Don't know where to start. Please help.
  2. jcsd
  3. Nov 19, 2011 #2
    I don't think it is a doppler effect question. I think it is just two echo times.
    You need a value for the speed of sound
  4. Nov 19, 2011 #3
    the speed of sound is 343m/s
  5. Nov 19, 2011 #4
    Now calculate the time to echo from 34cm, then from 44cm.
    The difference??
  6. Nov 19, 2011 #5
    had a miscalculation the first time I did it. Thanks.
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