Question

!!!!!!HELP!!!!!!!!!!

A train moving at a speed of 40.0 m/s sounds its whistle, which has a frequency of 500 Hz. Determine the frequency heard by a stationary observer as the train approaches the observer also find the frequency heard by the stationary observer as the train recedes from the observer.
I NEED THE FREQUENCY AS THE TRAIN RECEDES!!!

Answer 1

It depends on the speed of sound. The formula for receding sources is
f'=f(V/(V+Vsource)). For sound at speed V=346m/s the frequency is 448.2Hz