A uniform disc of mass 300 kg is rotating freely about a vertical axis through its centre at a constant angular velocity `omega_(0)`. A boy of mass 30 kg starts from the centre and moves along a radius to the edge of the disc. Angular velocity of the disc ill now become

Options

A. `(omega_(0))/(6)`
B. `(omega_(0))/(5)`
C. `(4omega_(0))/(5)`
D. `(5 omega_(0))/(6)`

Answer

D

Explanation

As `Sigma tau =0` , angular momentum remains conserved `:`
`:. L=(0+(300R^(2))/(2))`
`omega_(0)=((300R^(2))/(2)+30R^(2)).omega`
`=150 omega _(0)=180 omega`
`rArr omega = 5/6 omega _(0) Ans. `