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5.Work, Energy, Power and Collision
medium
A simple pendulum oscillates in a vertical plane. When it passes through the mean position, the tension in the string is $3$ times the weight of the pendulum bob. What is the maximum displacement of the pendulum of the string with respect to the vertical ......... $^o$.
A
$30$
B
$45$
C
$60$
D
$90$
Solution
(d) Tension at mean position, $mg + \frac{{m{v^2}}}{r} = 3\,mg$
$v = \sqrt {2gl} $…$(i)$
and if the body displaces by angle $\theta$ with the vertical then $v = \sqrt {2gl(1 – \cos \theta )} $…$(ii)$
Comparing $(i)$ and $(ii)$, $\cos \theta = 0$
$⇒$ $\theta = 90^\circ $
Standard 11
Physics