Question

A rod is lying still on a table which is also at rest as observed from ground's frame of reference. The net torque on the rod is zero with respect to?

• A. Only about the centre of mass of the rod
• B. Only about points on the rod.
• C. Only about points on the ground.
• D. None of these

Answer 1

The correct option is D None of these

It is already conveyed that the rod is in rotational and translational equilibrium with respect to the ground. Thus the net torque on it should be zero about any point in the whole universe! Because if it wasn't the case and suppose you found a point about which the net torque is non-zero, the rod should have some angular acceleration with respect to that particular point which is evidently not the case.