Q. If there is change of angular momentum from $J$ to $5\ J$ in 5 s, then the torque is
A) $\frac{3J}{5}$
B) $\frac{4J}{5}$
C) $\frac{5J}{4}$
D) None of these
Explanation
(b) We know that rate of change of angular momentum $(J)$ of a body is equal to the external torque $(\tau)$ acting upon the body.
$ie$. $\frac{dJ}{dt} = \tau$
Given, $J_{1} = J,\ \ J_{2} = 5J$
$\therefore$ $\mathrm{\Delta}J = J_{2} - J_{1} = 5J - J = 4J$
Hence, $\tau = \frac{4}{5}J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.