Question

The angular momentum of a flywheel having a moment of inertia of $0.4kg{m}^2$ decreases from 30 to 20 kg $m^2/s$ in a period of 2 second. Find the average torque in Nm acting on the flywheel during this period.

Answer 1

Given ,
Angular momentum changes from $30$ to $20$ $kg\frac{m^2}{s}$
and time taken $=2$ seconds.
Average torque =|$\frac{\Delta L}{\Delta t}$|
$\Rightarrow$ Average torque=|$\frac{-10}{2}$|=|$-5$|=$5$$kg\frac{m^2}{s^2}$