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Doppler Effect- small question on formula setup.

  • Thread starter Muntaballs
  • Start date
  • #1

Homework Statement



The security alarm on a parked car goes off and produces a frequency of 958 Hz. The speed of sound is 343 m/s. As you drive toward this parked car, pass it, and drive away, you observe the frequency to change by 95 Hz. At what speed are you driving?



Homework Equations


Doppler effect formula:
F=Fo [(Vsound- Vobserver)/(Vsound-Vsource)]




The Attempt at a Solution



This should be an easy problem but I just dont know how to setup the equations. I need to find the velocity, but I dont know how to solve for V.

863=958 [(343-V)/(343-0)]

How do I solve for Velocity? I dont know how to rearrange the formula so that V is isolated on one side of the equation.... Please help?
 

Answers and Replies

  • #2
Delphi51
Homework Helper
3,407
10
Use the formula twice. Once for the higher f observed when moving toward the source. Again for the lower f observed when moving away. Write that the higher f minus the lower f = 95. It is straightforward to solve that for v.
 

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