ICSE Class 10 Physics 2019 Solved Paper

Question : 49 of 74

Marks: +1, -0

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}

, find the distance between the cliff and the observer.

Solution:

Time taken for 4 vibrations of the pendulum

=1 {\ sec}

Time taken for 1 vibrations of the pendulum

=\;{1}/{4} {\ sec}

∴

Time taken for 6 vibrations of the pendulum

=\;{1}/{4} × 6=1.5 {\ sec}

We know,

v=\;{2 d}/{t}

d=\;{v t}/{2}

∴ \;\; d=\;{340 × 1.5}/{2}=255 {\m}

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