A railroad train is travelling at 30 m/s in still air. The frequency of the note emitted by locomotive whistle is 500 Hz. What is the frequency of the sound waves heard by a stationary listener (a) in front of the train and (b) behind the train? (speed of sound is 345m/s.)

Explanation

(a) In front of the train:
`=f'=f((v-V_0)/(c-V_S))=f((c-0)/(c-30))`
`impliesf'=(500xx345)/(345-30)=547.62Hz`
(b) Behind the train:
`f'=f((c-0)/(c-(-30)))=(500xx345)/(375)=460Hz`