A girl sits on a rolling chair, when she stretch her arms horizontally, her speed is reduced.
Principle of conservation of angular momentum is applicable in this situation.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Answer

A

Explanation

(a) If friction in the rotational mechanism is neglected, there is no extermal torque about the axis of rotation of the chair and hence `I omega` is constant. Where `I` is constant, where `I` is moment of inertoa and `omega` is angular velocity. Stretching the arms increases `I` about the rotation , results in decreasing the angular speed `omega`. Bringing the arms closer, body has the opposite effect.