Question

A boy standing at some distance from a cliff claps his hands and heard an echo 3 s later. What is the distance of the cliff from the boy, if speed is 340m/s :

• A. 226 m
• B. 510 m
• C. 453 m
• D. 1020 m

Answer 1

The correct option is B 510 m

Let $d$ be the distance of cliff from the boy . Therefore total distance covered by sound to go to cliff and come back to boy after reflection from cliff , $=2d$ ,

given $v=340m/s,t=3s$ ,

we have , distance=speed$\times time$ ,

$2d=v\times t=340\times 3$ ,

or $d=340\times 3/2=510m$