In the absence of external torque for a body revolving about any axis, the quantity that remains constant is

$A$ disc is rotating with an angular speed of $\omega$. If a child sits on it,which of the following is conserved?

$A$ solid sphere is rotating in free space. If the radius of the sphere is increased while keeping its mass constant,which of the following quantities will remain unaffected?

$A$ uniform disc of mass $100 \ kg$ and radius $2 \ m$ is rotating at $1 \ rad/s$ about a perpendicular axis passing through its centre. $A$ boy of mass $60 \ kg$ standing at the centre of the disc suddenly jumps to a point which is $1 \ m$ from the centre of the disc. The final angular velocity of the boy (in $rad/s$) is

Explain with illustration the pure translation and combination of translation and rotation motion of a rigid body.

$A$ cubical block of side $a$ is moving with velocity $v$ on a horizontal smooth plane as shown. It hits a ridge at point $O$. The angular speed of the block after it hits $O$ is