Question

A boy stands between the two walls and claps his hands as shown below:

If $x$ is less than $60m$ and the time between the first and the second echo is $0.25s$, then calculate the distance $x$. (Velocity of sound in air is 344 $m{s}^{-1}$)

• A. 36m
• B. 34m
• C. 40m
• D. 17m

Answer 1

The correct option is D

17m

Speed of sound = $344m/s$

Time taken for hearing the first echo = $\frac{2x}{344}$

Time taken for hearing the second echo = $\frac{120}{344}$
Time diffrence for hearing the echo =Time taken for hearing the second echo- Time taken for hearing the first echo

Hence, Time diffrence for hearing the echo =$\frac{120}{344}$ - $\frac{2x}{344}$= $0.25s$

$\Rightarrow 120-2x=86$

$\Rightarrow x=17m$