Question

A bus is moving towards a huge wall with a velocity of 5 ms^-1 . The driver sounds a horn of frequency 200 Hz. The frequency of the beats heard by a passenger of the bus will be ________Hz (Speed of sound in air  342 ms^-1). 

Answer 1

u_s = + 5 m/s, u₀ = -5m/s, v = 342 m/s

The observer and source are moving towards each other. The image of the source serves as source of reflected sound.

 Frequency of beats = 206 - 200 = 6 Hz