A Meery -go-round, made of a ring-like plarfrom of radius `R and mass M`, is revolving with angular speed `omega`. A person of mass `M` is standing on it. At one instant, the person jumps off the round, radially awaay from the centre of the round (as see from the round). The speed of the round after wards is

Options

A. `2 omega`
B. `omega`
C. `omega//2`
D. `0`

Answer

A

Explanation

When the person jumps off the round, radially away from the centre, no torque is exerted i.e. `tau = 0`.
According to the principle of conservation of angular momentum, `I xx omega =` constant. As mass reduces to half (from `2 M` to `M)`, moment of inertia `I` becomes half. Therefore, `omega` must become twice `(=2 omega)`.