Question

The angular momentum of a system of particles is not conserved :

• A. when a net external force acts upon the system
• B. when a net external torque is acting upon the system
• C. when a net external impulse is acting upon the system
• D. none of the above

Answer 1

Answer: (B)

when a net external torque is acting upon the system

Answer 2

By the principle of conservation of angular momentum,
when no external torque is acting upon a body rotating about an axis,
then the angular momentum of the body remains constant.
$J=I\,\omega =$ constant In our case external torque is acting then angular momentum is not conserved.