Question

The speed limit for a vehicle on road is 120 km/hr. A policeman detects a drop of 10% in the pitch of horn of a car as it passes him. Is the policeman justified in punishing the car driver for crossing the speed limit?

(Given: Velocity of sound = 340 m/s).

Answer 1

Given: Speed limit, v_L = 120 km/hr

n’_A = n_A – \(\frac{10}{100}\) n_A = 0.9 n_A

Velocity of sound, v = 340 m/s

To Find: Velocity of source (v_s)

Calculation:

Dividing formula (i) by (ii),