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Question: Answered & Verified by Expert
A simple pendulum of length $L$ swings in a vertical plane. The tension of the string when it makes an angle $\theta$ with the vertical and the bob of mass $m$ moves with a speed $v$ is $\mathrm{fg}$ is the gravitational acceleration)
PhysicsMotion In Two DimensionsWBJEEWBJEE 2015
Options:
  • A $m v^{2} / L$
  • B $m g \cos \theta+m v^{2} / L$
  • C $m g \cos \theta-m v^{2} / L$
  • D $m g \cos \theta$
Solution:
1192 Upvotes Verified Answer
The correct answer is: $m g \cos \theta+m v^{2} / L$
The situation is given below


For motion along a vertical circular track, the required centripetal force is along the radius and towards the centre of the circle is given by $T-m g \cos \theta=\frac{m v^{2}}{L}$
$\Rightarrow \quad T=\frac{m v^{2}}{L}+m g \cos \theta$

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