Question

SUNIL is standing between two walls. The wall closest to him is at a distance of 360meters. If he shouts he hears the first echo after 4second and another after another 2 second What is the velocity of sound in air? What is the distance between the two walls

Answer 1

Wall closest to him will listen the echo first...

Therefore,
Distance, d1 = 360m
time taken, t1 = 4s/2s = 2s

Speed = d1/t1
= 360/2
= 180m/s -------- (i)
Case ||:
Distance, d2 = ?
time taken, t2 = t1 + 2 / 2 = 4+2/2 = 3s (As it he heard the second echo after 2seconds)
speed = 180m/s (by eq.{i}
Distance = Speed × time
= 180 × 3
Distance of second wall from sunil is = 540m = d2;

Distance between two walls = d1 + d2
= 360 + 540
= 900m

Answer 2

Correct question:

- Sunil is standing between two 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 2 seconds .

Answer:

Velocity = 330m/s

Distance between two walls = 1650 meters

Given information:

Suppose sunil is standing is a room between 2 walls.

Wall closest to sunil is at distance of 660 meters.

And, If he shouts, then he heard the Echo from his nearest wall in 4 seconds.

And, Another wall echo is heard in next 2 seconds.

To find: i) Velocity of sound in Air ?

             ii) Distance between two walls

Explanation:

Method I :

i) Velocity of sound in Air:

Velocity = Distance /  Time/2 (Because we heard sound after getting reflected back)

Velocity = 660 /  2

Velocity = 330 m/s

Therefore, Velocity of sound in Air is 330 m/s.

ii) What is the distance between two walls ?

For first wall,

Distance = ?

Velocity = 330 m/s

Time = 4 seconds

Distance = Velocity * time

Distance = 330 * 4

Distance = 1320 meters -------- (i)

For second wall,

Distance = ?

Time = 2 seconds

Velocity = 330 m/s

Distance = Velocity * 2/ time

Distance = 330 * 1

Distance = 330 meters ------- (ii)

Adding equation (i) and (ii),

Distance between 1st wall  + Distance between 2nd wall = Distance between two walls

Distance between two walls = 1320 + 330

Distance between two walls = 1650 meters

Therefore, Distance between 2 walls is 1650 meters.

Method II :

i) Velocity of sound:

Velocity of sound = Distance/time

Velocity of sound = 660/2

Velocity of sound = 330 m/s

ii) Distance between two walls:

Distance = Velocity * total time

Distance = 330 * 6

Distance = 1650 meters