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Question
A pendulum has a frequency of 5 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears echo from the cliff after 8 vibrations of the pendulum. If the velocity of sound in air is 340 ms-1, find the distance between the cliff and the observer.
Solution
Speed of sound in air v = 340 m/s-1
Time taken for 8 vibration t = `8/5` sec
Distance between cliff and observer
d = `(vt)/2`
= `(340 xx 8)/(2 xx 5)`
= 272 m
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