Question

Suppose you are standing on the edge of a spinning platform and step off at right angles to the edge (radially outward). Now consider it the other way. You are standing on the ground next to a spinning carousel and you step onto the platform at right angles to the edge (radially inward) .Then,

• A. there is no change in rotational speed of the carousel in either situation
• B. there is a change in rotational speed in the first situation but not the second
• C. there is a change in rotational speed in the second situation but not the first
• D. there is a change in rotational speed in both instances

Answer 1

The correct option is D there is a change in rotational speed in both instances

The moment of inertia is changed in both the cases. In first case the moment of inertia is decreased as the revolving mass is reduced thereby increasing the angular velocity and it is the other way round in the second case. Thus there is a change in rotational speed in both instances. We are using the principle of conservation of angular momentum $I_1{\omega }_1=I_2{\omega }_2$.