Chapter 14, Problem 26P

A train is moving past a crossing where cars are waiting for it to pass. While waiting, the driver of the lead car becomes sleepy and rests his head on the steering wheel, unintentionally activating the car’s horn. A passenger in the back of the train hears the horn’s sound at a frequency of 428 Hz and a passenger in the front hears it at 402 Hz. Find (a) the train’s speed and (b) the horn’s frequency, assuming the sound travels along the tracks.