Question

A ballet dancer, dancing on a smooth floor is spinning about a vertical axis with her arms folded with an angular velocity of 20 rad/s. When she stretches her arms fully, the spinning speed decrease in 10 rad/s. If I is the initial moment of inertia of the dancer, the new moment of inertia is

• A. 2I
• B. 3 I
• C. 1/2
• D. I / 3

Answer 1

Answer: (A)

2I

Answer 2

Here, angular momentum is conserved.

Initial angular momentum = final angular

Momentum

]

Where I’ is new moment of inertia,