Doppler Effect- small question on formula setup.

AI Thread Summary
To determine the speed of the observer driving toward and away from a parked car's alarm, the Doppler effect formula is applied. The observed frequency changes from 958 Hz to 863 Hz, indicating a 95 Hz difference. The equation can be set up using the formula for both approaches and departures from the sound source. By isolating the velocity variable and solving the equations, the speed can be calculated. The problem emphasizes the importance of using the Doppler effect formula in both scenarios to find the observer's speed.
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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 don't know how to setup the equations. I need to find the velocity, but I don't know how to solve for V.

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

How do I solve for Velocity? I don't know how to rearrange the formula so that V is isolated on one side of the equation... Please help?
 
Physics news on Phys.org
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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