Question

A pendulum has a frequency of 4 vibration per second .An observer starts the vibration and fire gun simultaneously .He hear the Echo from the Cliff after 6 vibration of the pendulum if the velocity of the sound in air is 340 Meter per second find the distance between the Cliff and observe

Answer 1

1 second = 4 vibrations

1 vibration = 1/4 second

6 vibrations = 6/4 = 3/2 = 1.5 seconds

Therefore it take 1.5 seconds for the sound wave to return to the observer after reflecting from the cliff ..

T=2d/v

d = (1.5 x 340)/2

d = 255 m

Answer 2

Time=1.5 sec

V=340 m per sec

D=vt/2

Substitute for answer