Question

A man standing at a distance from a hill fires a gun an hears its echo after 4.7 sec. He , then, moves 300 m closer to the hill and fires the gun. Echo of this sound is heard after 2.9 sec. What is the velocity of sound?

Answer 1

Suppose the man was initially ‘x’ m away from the hill. Let the speed of sound be ‘v’.

Initially, sound comes back to the man in 4.7 s, so,

4.7 = 2x/v

=> x = 4.7v/2

Then after moving 310 m towards the hill, sound comes back in 3 s,

2.9 = 2(x-300)/v

=> 2.9 v = 2x – 600

=> 2.9 v = 4.7v – 600

=> v = 333.3 m/s

This is the speed of sound.