COMEDK2025PhysicsRotational MotionActual
A rigid body is said to be in rotational equilibrium:
Options
- AIf the net external torque acting on the body is zero
- BIf the net external force acting on the body is zero
- CIf the net internal force acting on the body is zero
- DIf the net angular momentum of the body is zero
Correct answer
A. If the net external torque acting on the body is zero
Step-by-step solution
A rigid body is in rotational equilibrium when it does not undergo any angular acceleration. According to Newton's second law for rotation, the net external torque _ ext acting on a body is equal to the rate of change of its angular momentum, given by _ ext = d L dt . For rotational equilibrium, the angular acceleration must be zero, which implies that the net external torque acting on the body must be zero, i.e., _ ext = 0 . The condition of net external force being zero corresponds to translational equilibrium, n