- #1

Elias Waranoi

- 45

- 2

## Homework Statement

A stationary police car emits a sound of frequency 1200 Hz that bounces off a car on the highway and returns with a frequency of 1250 Hz. The police car is right next to the highway, so the moving car is traveling directly toward or away from it. (a) How fast was the moving car going? Was it moving toward or away from the police car?

## Homework Equations

ƒ

_{L}= ƒ

_{S}(v - v

_{L})/(v - v

_{S})

## The Attempt at a Solution

The returning frequence is larger so its wave length has to be smaller which tells us that the car is moving towards the police car.

v

_{S}= v - vƒ

_{S}/ƒ

_{L}= 13.76 m/s

The correct answer is 7.02 m/s.

What am I doing wrong?