A uniform thin bar of mass `6 m` and length `12 L` is bend to make a regular hexagon. Its moment of inertia about an axis passing through the centre of mass and perpendicular to the plane of the hexagon is :

Options

A. `20 mL^2`
B. `6 mL^2`
C. `(12)/(5) mL^2`
D. `30 mL^2`

Answer

A

Explanation

(a) `x = 2L cos 30^@ = L sqrt(3)`
`I = 6((m(2 L)^2)/(12) + mx^2) = 20 mL^2`
.