A smoothh disc is rotating with uniform angular speed `omega` about a fixed vertical axis passing through its centre and normal to its plane as shown. A small block of mass m is gently placed at the periphery of the disc. Then (pickup the correct alternative or alternatives)

Options

A. In comparision to `omega` the angular speed of the disc now increases
B. in comparision to `omega` the angular speed of the disc now decreases
C. in comparision to `omega` the angular speed of the disc now remains same
D. the block will move tangentially and fall of the disc.

Answer

B

Explanation

the only force block exerts on disc is parallel to axis of rotation of disc. This additional of disc. This additional force does not cause any torque on disc. Hence angular momentum of disc remains same.
Since there is no friction between block and disc, the block remains in its position.