Question

When a train is at rest, both a passenger on the train and a ticket seller at the station agree that the trains whistle produces sound at a frequency of 120 Hz. When the train is moving away from the station at 15 m/s, the passenger hears a frequency of ___ Hz and the ticket seller hears a frequency of ____ Hz.

A) 120, 125 

B) 115, 120 

C) 120, 120 

D) 115, 115 

E) 120, 115

Answer 1

The correct option is: (E) 120, 115

Explanation:

Doppler effect. Since the passenger is on the train moving with the sound, the frequency is unaltered, but since the sound is moving away from the station, people at the station should hear a lower frequency.