Question

If torque acting on a system is zero, the quantity that remains constant is

• A. force
• B. linear momentum
• C. angular momentum
• D. angular velocity

Answer 1

The correct option is C angular momentum

As we know,
$\overrightarrow{\tau }=\frac{d\overrightarrow{L}}{dt}$
where $\overrightarrow{\tau }=$ torque
$\overrightarrow{dL}=$ change in angular momentum
If $\overrightarrow{\tau }=0,\frac{d\overrightarrow{L}}{dt}=0$
Hence, $\overrightarrow{L}=$ constant
So, if net torque on the system about an axis is zero, then angular momentum of that system about that axis is conserved.
Hence, option (c) is correct.