Question

A state trooper chases a speeder along a straight stretch of road; both vehicles move at 164 km/h. The siren on the trooper's vehicle produces sound at a frequency of 475 Hz and the speed of sound in the air is 343 m/s. What is the Doppler shift in the frequency heard by the speeder

Answer 1

The Doppler effect can be calculated by:

f' = ((v - v0)/(v -vs))*f

where f is the frequency, v is the velocity of the wave, v0 is the velocity of the observer and vs is the velocity of the source.

But the observer and the source move at the same speed (bot cars have the same velocity), so here we will not see the doppler effect the relative velocity between the cars is 0m/s.

This means that the frequency that will be heard by the speeder is 475hz