Question

A police car moving at 22 m/s chases a motorcyclist. The police man sounds his horn of frequency 176 Hz, while both of them move towards a stationary siren of frequency 165 Hz. Calculate the speed of motorcyclist if it is given that he does not hear any beat (speed of sound in air is 330 m/s)

• A. 33 m/s
• B. 22 m/s
• C. 11 m/s
• D. zero

Answer 1

The correct option is B 22 m/s

$n_1=n_2\Rightarrow \frac{v-v_m}{v-v_c}{n}^{\prime }=\frac{v+v_m}{v-v_s}n\Rightarrow \frac{v-v_m}{v-22}\times 176=\frac{v+v_m}{v}\times 165\Rightarrow v_m=22m/s$