Question

A truck moving at 36 m/s passes a police car moving at 45 m/s in the opposite direction. If the frequency of the siren is 500 Hz relative to the police car, what is the change in frequency (in Hz) heard by an observer in the truck as the two vehicles pass each other? (The speed of sound in air is 343 m/s.)

Answer 1

Answer:

change in frequency is 636 Hz

Explanation:

given data

speed v1 = 36 m/s

speed v2 = 45 m/s

frequency f = 500 Hz

speed of sound s = 343 m/s

to find out

what is the change in frequency

solution

we know here change of frequency formula that is

frequency = $\frac{s+v1}{s+v2}$ (f)   ...................1

put here value in equation 1

and we take v2 = -45 because opposite direction

frequency = $\frac{s+v1}{s-v2}$ (f)

frequency = $\frac{343+36}{343-45}$ (500)

frequency = 636

so change in frequency is 636 Hz