Question

A boy stands at a distance of 165 m from a cliff. He claps his hand and hears an echo. If the speed of sound in air is 330 m/s, after how long does he hear the echo?

Answer 1

Given: Distance between the boy and the cliff = d = 165 m
Speed of sound in air = v = 330 m/s
Let us assume that the time taken for the sound of the clap (echo) to reach the boy is t.
Total distance travelled by the sound = 2d
Time = Distance / Speed
t = 2d / v
t = (2 x 165) / 330
t = 1 sec
Thus, after one second, the boy will hear the echo.