Q. A ball of mass $0.1\ kg$ is suspended by a string. It is displaced through an angle of $60{^\circ}$ and left. When the ball passes through the mean position, the tension in the string is
A) $19.6\ N$
B) $1.96\ N$
C) $9.8\ N$
D) Zero
Explanation
(b) $T = mg + \frac{mv^{2}}{l} = mg + \frac{m}{l}\lbrack 2gl\left( 1 - \cos\theta \right)\rbrack$
$= mg + 2mg\left( 1 - \cos{60{^\circ}} \right) = 2mg = 2 \times 0.1 \times 9.8 = 1.96N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.