The conservation of angular momentum demands that

Options

A. the external force on the system must be zero
B. the external torque on the system must be zero
C. Both the external force as well as the external torque must be zero
D. Neither of them must be zero

Answer

B

Explanation

From law of conservation of angular momentum, if no external torque acts on a system, then total vector sum of angular momentum of different particles of the system remains conserved.
`tau_("ext") =0` then `(dL)/(dt)=0`