A horizontal disc rotates freely with angular velocity `omega` about a vertical axes through its centre. A rig having the same mass and radius as the disc, is now gently placed coaxially on the disc. After some time, the two rotate with a common angular velocity. then.

A horizontal disc rotates freely about a vertical axis through its centre. A ring, having the same mass and radius as the disc, is now gently placed on the disc. After some time, the two rotate with a common angular velocity, then

A disc rotates freely with rotational kinetic energy E about a normal axis through centre. A ring having the same radius but double the mass of disc is now, gently placed on the disc. The new rotational kinetic energy of the system would be

A disc of mass m and radius r is rotating with angular velocity, on a frictionless horizontal plane about a vertical axis passing through its centre. A ring of same mass and radius is gently placed on it in such a way that centres of both coincide. After some time it is found that both attain a common angular velocity