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Doppler Effect of a blown whistle

  • Thread starter lha08
  • Start date
  • #1
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Homework Statement


A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev/min. A listener standing some distance away in the plane of rotation hears frequencies in the range ____?
(speed of sound=340 m/s)
a) 436 to 586
b) 426 to 574
c) 426 to 584
d) 436 to 674


Homework Equations





The Attempt at a Solution


I'm not really sure how to approach this particular problem...i'm lost especially for the units and what to do with the string...thanks
 

Answers and Replies

  • #2
rl.bhat
Homework Helper
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when the whistle is moving in a horizontal circle, at two points on the circle the whistle is moving either towards the observer or away from him. Apply Doppler effect to find the frequencies.
 
  • #3
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when the whistle is moving in a horizontal circle, at two points on the circle the whistle is moving either towards the observer or away from him. Apply Doppler effect to find the frequencies.
okay i understand that part, but how do i convert 400 rev/min and for the length of the string do i use C=2(pi)radius and solve for r?
 
Last edited:
  • #4
rl.bhat
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Velocity v = 2*pi*n*r where n is the number revolution per second.
 
  • #5
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Velocity v = 2*pi*n*r where n is the number revolution per second.
but how do i solve for the radius using the length of the string?
 
  • #6
rl.bhat
Homework Helper
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but how do i solve for the radius using the length of the string?
Length of the string itself is the radius.
 

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