Kinematics Question 559

Question: 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 [Or it’ssa JEE 2002]

Options:

A) $ 30^{o} $

B) $ 45^{o} $

C) $ 60^{o} $

D) $ 90^{o} $

Show Answer

Answer:

Correct Answer: D

Solution:

Tension at mean position, $ mg+\frac{mv^{2}}{r}=3mg $

$ v=\sqrt{2gl} $ -(i) and if the body d it’splaces by angle q with the vertical then

$ v=\sqrt{2gl(1-\cos \theta )} $ -(ii) Comparing (i) and (ii), $ \cos \theta =0 $

therefore $ \theta =90{}^\circ $



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