Physics
A pendulum has a frequency of 4 vibrations per second. An observer 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-1, find the distance between the cliff and the observer.
Work, Energy & Power
ICSE 2019
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Answer
Echo is heard after 6 vibrations of pendulum. Since frequency of pendulum is 4 vib per sec, so the time taken for the echo to be heard is t = = 1.5 s.
If d is the distance between the cliff and the observer, then velocity of sound V =
Substituting the values in the equation above:
Hence, distance between the cliff and the observer = 255 cm
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