Question

The following motion is based on the law of conservation of angular momentum
A) rotation of top
B) diving of a diver
C) rotation of ballet dancer on smooth horizontal surface
D) a solid sphere that rolls down on an inclined plane

Identify the wrong statement:

• A. In rotating a top, angular momentum is conserved.
• B. When a diver dives using a board, angular momentum is conserved.
• C. In rotation of a ballet dancer on a smooth horizontal surface, angular momentum is conserved.
• D. When a solid sphere rolls down an inclined plane, angular momentum is conserved.

Answer 1

The correct option is D When a solid sphere rolls down an inclined plane, angular momentum is conserved.

In rotating a top, diving of a diver and rotation of a dancer, there is no external torque involved. Thus angular momentum is conserved.

But when a sphere rolls down an incline, external torque (torque due to friction) is involved.