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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.
Solution
v =4HZ vs = 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
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