The moment of inertia of a circular dics about one of its diameters is l. What will be its moment of inertia about a tangent parallel to the diameter?

Options

A. `4l`
B. `2l`
C. `(5l)/(2)`
D. `5l`

Answer

D

Explanation

The moment of inertia of a circular disc about one of its diameters, `l=(1)/(4)MR^(2)`
`therefore" "MR^(2)=4l`
`therefore" "` Ml about a tangent parallel to the diamater,
`l=l_(CM)+MR^(2)` (According to the parallel axes theorem)
`=(1)/(4)MR^(2)+MR^(2)=(5MR^(2))/(4)=5l" "(therefore MR^(2)=4l)`