Doppler Effect- small question on formula setup.

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SUMMARY

The discussion centers on applying the Doppler effect formula to determine the speed of a vehicle approaching and then moving away from a stationary sound source. The frequency of the sound produced by the alarm is 958 Hz, and the observed frequency changes by 95 Hz. Using the formula F = Fo [(Vsound - Vobserver) / (Vsound - Vsource)], the user is guided to set up two equations: one for the frequency observed while approaching the source and another for the frequency observed while receding. The difference between these two frequencies equals 95 Hz, allowing for the calculation of the observer's speed.

PREREQUISITES
  • Understanding of the Doppler effect and its formula.
  • Basic algebra skills for rearranging equations.
  • Familiarity with sound wave properties, including frequency and speed of sound.
  • Knowledge of how to apply physics concepts to real-world scenarios.
NEXT STEPS
  • Study the derivation of the Doppler effect formula in various contexts.
  • Practice solving problems involving the Doppler effect with different frequencies and speeds.
  • Explore the impact of medium changes on sound speed and frequency perception.
  • Learn about applications of the Doppler effect in fields such as astronomy and radar technology.
USEFUL FOR

Students studying physics, particularly those focusing on wave phenomena, as well as educators seeking to explain the Doppler effect in practical scenarios.

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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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