Question

The siren of a police car at rest emits at a predominant frequency of 1980 Hz. What frequency will you hear if you are at rest and the police car moves at 34.3.0m/s (a) toward you, and (b) away from you? Please Explain

Answer 1

(a) 1782 Hz (b) 2178 Hz

Step-by-step explanation:

The predominant frequency =1980 Hz

The speed of the police car =34.3 m/sec

The speed of sound in air =343 m/sec

(a) When the car moves towards you

According to Doppler's effect

`f=f_0(v-v_s)/(v)=1980* (343-34.3)/(343)=1782Hz`

(b) When the car moves away from you

`f=f_0(v+v_s)/(v)=1980* (343+34.3)/(343)=2178Hz`