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Find difference in echo times, doppler shift?

  • #1

Homework Statement


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?


Homework 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
λ=v/f

Doppler shift (moving away from observer)
Fobs=(fsource)/{1+(Vsource/Vsound)}


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.
 

Answers and Replies

  • #2
1,506
17
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
 
  • #3
the speed of sound is 343m/s
 
  • #4
1,506
17
Now calculate the time to echo from 34cm, then from 44cm.
The difference??
 
  • #5
had a miscalculation the first time I did it. Thanks.
 

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