String of pendulum of length l is displaced through {90^o} from vertical and released. Then minimum

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5.Work, Energy, Power and Collision

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The string of pendulum of length $l$ is displaced through ${90^o}$ from the vertical and released. Then the minimum strength of the string in order to withstand the tension, as the pendulum passes through the mean position is

A

$mg$

B

$3mg$

C

$5\,mg$

D

$6\,mg$

Solution

(b) $T = mg + \frac{{m{v^2}}}{l}$ $ = mg + 2mg = 3mg$

where $v = \sqrt {2gl} $ from $\frac{1}{2}m{v^2} = mgl$

Standard 11

Physics

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