A police car with a siren of frequency 8 kHz is moving with uniform velocity 36 km/h towards a tall building which reflect the sound waves. The speed of sound in air is 320 m/s. What is the frequency of the siren heard by the car driver ?

A police car with a siren of frequency 8 kHz is moving with uniform ve

1.	A police car with a siren of frequency 8 kHz is moving with uniform velocity 36 km/h towards a tall building which reflect the sound waves. The speed of sound in air is 320 m/s. What is the frequency of the siren heard by the car driver ?
Answer» Solution :(a) Frequency RECEIVED by the BUILDING. `f. = ((V)/(v-v_c))` The wall (source) reflect this frequency,So frequency heard by the car DRIVER is `f..=((v+v_c)/v)f. = ((v+v_c)/v)(v/(v-v_c))f` `= ((v + v_c)/(v-v_c)) f= ((320 + 10)/(320 - 10)) xx 8 kHz = 33/31 xx 8= 8.5 kHz`