Question

An observer stands at a distance of 850 m from the cliff and fires a gun. After what time will he hear the echo if sound travels at a speed of $350m{s}^{-1}$ in air?

• A. 6.89 s
• B. 4.88 s
• C. 2.93 s
• D. 4.86 s

Answer 1

The correct option is D

4.86 s

Speed of sound = $350m{s}^{-1}$
Distance = 850 m
Here, $v=350m{s}^{-1},d=850m$,

This is a case of an echo, sound travels back and forth, and hence the distance is taken twice the distance, $2d=c\times t$

$t=\frac{2d}{c}$

$=\frac{(2\times 850)}{350}=4.86s$.