The doppler shift was first tested in 1845
by the french scientist b. ballot. he had
a trumpet player sound a 414 hz note while
riding on a flat-car pulled by a locomotive. at
the same time, a stationary trumpeter played
the same note. ballot heard 4 beats/s.
how fast was the train moving toward him?
the speed of sound in air is 343 m/s .
answer in units of m/s