Question

John fires a gun towards a hill and hears its echo after $5$ seconds. He then moves $320m$ towards the hill and fires his gun again. This time he hears the echo after $3$ seconds. Calculate the velocity of sound.

Answer 1

t= 5 s

At the beginning, let s be the distance between John and the hill

$\therefore v=\frac{2s}{t}=\frac{2s}{5}$

John then moves 320 m towards the hill in 3s,

$\therefore v=\frac{2(s-320)}{t^{\prime }}=\frac{2(s-320)}{3}$

Since velocities are same,

$\therefore \frac{2s}{5}=\frac{2(s-320)}{3}$

or, s = 800m

velocity = $v=\frac{2\times 800}{5}=320m/s$