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A simple pendulum performs S.H.M. of period 4 seconds. How much time after crossing the mean position, will the displacement of the bob be one-third of its amplitude.

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Question

A simple pendulum performs S.H.M. of period 4 seconds. How much time after crossing the mean position, will the displacement of the bob be one-third of its amplitude.

Sum
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Solution

Data: T= 4 s, x = A/3

The displacement of a particle starting into SHM from the mean position is x = A sin wt = A sin `(2π)/"T"`t

∴ A sin `(2π)/"T"`t = `"A"/3`

∴ `(2π)/"T"`t = sin-1 0.3333 = 19.47° = `19.47xxπ/180`rad

∴ `2/4`t = `19.47/180`

∴ t = `19.47/90` = 0.2163 s

∴ The displacement of the bob will be one-third of its amplitude 0.2163 s after crossing the mean position.

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Chapter 5: Oscillations - Exercises [Page 130]

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Balbharati Physics [English] Standard 12 Maharashtra State Board
Chapter 5 Oscillations
Exercises | Q 13. | Page 130

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