Question

A pendulum has a frequency of 4 vibrations per second. An oberver starts the pendulum and fires a gun simultaneously. He hears the echo from the cliff after 6 vibrations of the pendulum, if the velocity of sound in air is 340 m/s, find the distance betwen the cliff and the obsever.

Answer 1

v =4H_Z                  v_s = 340 m/s 

`T =1/4` sec

`t = 6 xx1/4 = 1.5 `sec

As echo is listened ;

`2d = v_s xx t`

`d =(v_s xx t)/2 = (340 xx 1.5 )/2 = 255`m