Physics Homework Help?

Question

In one of the original Doppler experiments, a tuba was played at a frequency of 53.0 Hz on a moving flat train car, and a second identical tuba played the same tone while at rest in the railway station.

What beat frequency was heard in the station if the train car approached the station at a speed of 19.0 m/s ?

Answer 1

The source frequency is 

The speed of the train car approaching the station is 

Doppler effect: Frequency observed of the train car approaching towards the stationary listener is .

Here  is the frequency of the sound heard by the listener.

 is the velocity of the source.

 is the velocity of the sound  and

 is the frequency of the sound emitted by the source.

The beat frequency is the difference between those two frequencies:

Beat frequency is