Question

Sunil is standing between two parallel walls. The wall closest to him is at a distance of 660m. If he shouts, he hears the first echo after 4s and another after another 2s.

1) What is the velocity of sound in air?

2) What is the distance between the two walls?

Answer 1

Given that,

The distance of wall closest to him is 660 m.

And first echo will be heard after 4 seconds.

1)

Thus, distance travelled by the sound in 4second would be = 660*2

Hence, velocity of sound in air = 660*2/4= 330m/s

Hence, the velocity of sound in air would be 330m/s.

2)

The time required to hear second echo= 2+4= 6 seconds

Let distance travelled in 6s would be= 2*X

And velocity of sound in air is 330m/s.

Hence, we can write,

2*X= 330*6

Thus, X= 990m

Hence, the distance between the two walls is= 990+660= 1650m