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 = 344 m/sec
Time taken for hearing the echo = 0.25 sec
Distance travelled by sound = 344 $\times$ 0.25 = 86m
In 0.25 s, sound has to travel twice the distance b/w wall & the boy.

Hence the distance between the wall & the person $=\frac{86}{2}=43$
Distance x = 60 – 43
x = 17m