Q. The string of pendulum of length $l$ is displaced through $90{^\circ}$ 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) $6\ mg$
Explanation
(b) $T = mg + \frac{mv^{2}}{l} = mg + 2mg = 3mg$
Where $v = \sqrt{2gl}$ from $\frac{1}{2}mv^{2} = mgl$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.