Question

A girl rotates on swivel chair

(a) What happens to her angular speed when she stretches her arms .

(b) Name and state the conservation law applied for your justification .​

Answer 1

Answer:

When the girl stretches her arm, according to a law of conservation of angular momentum the distance from the axis of rotation increases and so a moment of inertia increases and thereby angular speed decreases.

Explanation:

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Answer 2

Answer:

(a) The angular speed of the girl decreases.

(b)The conservation of angular momentum. In the absence of net external torque, the total angular momentum is conserved or the total angular momentum of an isolated system remains constant both in magnitude and direction.

Explanation:

(a) When the girl stretches her arm the distance from the axis of rotation increases and so a moment of inertia increases and thereby angular speed decreases. This is in accordance with the conservation of angular momentum. i.e.

                          $I\omega=constant$   (1)

                          $I\propto\frac{1}{\omega}$      (2)

Where,

I=moment of inertia

ω=angukar speed

(b) The law applied over here is the law of conservation of angular momentum. It states that in the absence of an external torque, the total angular momentum is conserved or the total angular momentum of an isolated system remains constant both in magnitude and direction.

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