# The doppler effect

1. Feb 27, 2009

### dietcokegal

1. The problem statement, all variables and given/known data

A car moving at 35 m/s approaches a stationary whistle that emits a 220 Hz sound. The speed of sound is 343 m/s. What is the speed of sound relative to the driver of the car?

2. Relevant equations

fo = fs [1 +/- vo/v] / [1 +/- vs/v]

3. The attempt at a solution

Dont know how to do this problem at all. Im not understanding what the question is even asking for. I solved for the frequency that the observer in the car is hearing -- 242 Hz. Not sure how to figure out the question being asked.

2. Feb 27, 2009

### aeroengineer

Well, the speed of something relative to something else would be that something minus the value of the something else.

So it looks like all you need to do is subtract the speed of sound from the speed of the car (but remember that they are on a collision course, so you would really by adding the two velocities).

Eh, that's an oddly phrased question.