Question

A man standing in front of a vertical cliff fires a gun. He hears the echo after 3.5 seconds. On moving closer to the cliff by 84 m, he hears the echo after 3 seconds. Calculate the distance of the cliff from the initial position of the man.

Accepted Answer

Answer

Let the distance between cliff and initial position of the man be x m.

Total distance travelled by the sound = 2x

Time taken = 3.5 s

Speed of sound = 2x/3.5

When he moves 84 m closer to cliff

Distance travelled = 2(x - 84)

Time taken to hear echo = 3 s

Speed of sound = 2(x - 84)/3

Speed of sound is same in both the cases. So,

2x/3.5 = 2(x - 84)/3

7x - 588 = 6x

x = 588 m

The required distance = 588 m