Physics Two Dimensional Motion Question 89

Question: 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

[MP PMT 1986]

Options:

A) $ mg $ B)$ 3mg $ C) $ 5,mg $ D) $ 6,mg $

Show Answer

Answer:

Correct Answer: B

Solution:

$ T=mg+\frac{mv^{2}}{l} $

$ =mg+2mg=3mg $ where $ v=\sqrt{2gl} $ from $ \frac{1}{2}mv^{2}=mgl $