Rigid Body Dynamics Questions

The ratio of the radii of gyration of a circular disc to that of a circular ring, each of the same mass and radius, around their respective axes (passing through the center and perpendicular to the plane) is:

A thin rod of length $L$ and mass $M$ is bent at its midpoint into two halves so that the angle between them is $90^{\circ }$. The moment of inertia of the bent rod about an axis passing through the bending point and perpendicular to the plane defined by the two halves of the rod is:

A disk and a sphere of same radius but different masses roll off on two inclined planes of the same altitude and length. Which one of the two objects gets to the bottom of the plane first?

A uniform circular disc of radius $50\text{cm}$ at rest is free to turn about an axis which is perpendicular to its plane and passes through its centre. It is subjected to a torque which produces a constant angular acceleration of $2.0{\text{rad s}}^{-2}$. Its net acceleration in ${\text{ms}}^{-2}$ at the end of $2.0\text{s}$ is approximately: