Question

From a circular disc of radius R and mass 9 M , a small disc of radius R/3 is removed from the disc. The moment of inertia of the remaining disc about an axis perpendicular to the plane of the disc and passing through O is

A. `8 mR^(2)`
B. `4 mR^(2)`
C. `(40)/(9) mR^(2)`
D. `(37)/(9) mR^(2)`

Answer 1

Correct Answer - B
`I_("remaining") = I_("whole") - I_("removed")`
`I =(1)/(2) (9m) (R^(2)) -[(1)/(2)m ((R)/(3))^(2) + m((2R)/(3))^(2)]`
`I = 4mR^(2)`.