Question

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? (b) What frequency would the police car have received if it had been traveling toward the other car at 20.0 m/s?

Answer 1

(a): The moving car was going at Vo= 14.29 m/s moving toward the police car.

(b) If the police car had been traveling toward the other car at 20 m/s would receive a frequency of f''= 1327.39 Hz.

Step-by-step explanation:

V= 343 m/s

f= 1200 Hz

f'= 1250 Hz

Vo= ?

Vf= 0

f'= f* {(V - (Vo) / V}

clearing Vo:

Vo= 14.29 m/s (a)

f''= f* {(V - (Vo) / V - 20 m/s}

f''= 1327.39 m/s (b)