Question

A pendulum has a frequency of 5 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears the echo from the cliff after 8 vibrations of the pendulum. If the velocity of sound in air is 340 m $s^{-1}$, find the distance between the cliff and the observer.

Answer 1

Time taken for 1 vibration = s

Time taken for 8 vibrations = s

We know, $2d=vt$

Therefore,


D= [where d = distance between the observer and the cliff ]

V = velocity of sound
T= time taken for the sound to go and return


D = = 272 m

So the distance between the cliff and observer is 272