Question

An observer standing by the side of a highway estimates a drop of 20% in the pitch of the horn of a car as it crosses him. If the velocity of sound is 330 m/s, calculate the speed of the car.

Answer 1

Given : 

v = 330 m/s 

Let f₁ and f₂ be the apparent frequencies heard ty the observer, before and after the source crossing respectively.

Solving this we get v_s = 36.67 ms^-1.