A ballet dancer, dancing on a smooth floor is spinning about a vertical axis with her arms folded with 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

Question

A ballet dancer, dancing on a smooth floor is spinning about a vertical axis with her arms folded with 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) 2 I (B) 3 I (C) I / 2 (D) I / 3

Tardigrade Admin · Accepted Answer

Here, angular momentum is conserved. Initial angular momentum = Final angular momentum I × 20=I' × 10 Where I' is new moment of inertia I'=2 I

$2 I$

$3 I$

$I /2$

$I /3$

Here, angular momentum is conserved.
Initial angular momentum = Final angular momentum
$I \times 20 = I^{'} \times 10$
Where $I^{'}$ is new moment of inertia
$I^{'} = 2 I$

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

2I

3I

I/2

I/3

Here, angular momentum is conserved. Initial angular momentum = Final angular momentum I×20=I′×10 Where I′ is new moment of inertia I′=2I

$2 I$

$3 I$

$I /2$

$I /3$

Here, angular momentum is conserved.
Initial angular momentum = Final angular momentum
$I \times 20 = I^{'} \times 10$
Where $I^{'}$ is new moment of inertia
$I^{'} = 2 I$