Question

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

• A. $6.89s$
• B. $2.42s$
• C. $2.93s$
• D. $4.86s$

Answer 1

The correct option is D

$4.86s$

Speed of sound in air, v = $350m{s}^{-1}$
Distance of the cliff from the man, $d=850m$
Total distance covered by the sound to reach to the observer again =$2\times d=2\times 850m=1700m$
Let time taken to travel this distance be $t$
$t=\frac{2d}{v}$

$=\frac{\left(1700\right)}{350}=4.86s$.