Q. A body of mass $0.4\ kg$ is whirled in a vertical circle making $2\ rev/sec$. If the radius of the circle is $2\ m$, then tension in the string when the body is at the top of the circle, is
A) $41.56\ N$
B) $89.86\ N$
C) $109.86\ N$
D) $115.86\ N$
Explanation
(d) Tension at the top of the circle, $T = m\omega^{2}r - mg$
$T = 0.4 \times 4\pi^{2}n^{2} \times 2 - 0.4 \times 9.8 = 122.2N \approx 115.86N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.