Two uniform circular discs having the same mass and the same thickness but different radii are made from different materials. The disc with the smaller rotational inertia is

Options

A. The one made from the more dense material
B. The one made from the less dense material
C. The disc with the larger angular velocity
D. The disc with the larger torque

Answer

(b)

Explanation

The expression for moment of inertia of circular disc is given as,
`I=(1)/(2)MR^(2)`
=`(1)/(2)M((M)/(pitp))` `(because M=piR^(2)t p implies R^(2)=(M)/(pitp))`
` (1)/(2) (M^(2))/(pitp)` When the thickness and mass becomes equal, we get,
` I=propto(1)/(p)` When the disc with the smaller rotational inertia is the one made from the denser material.