Seven identical circular planar disks, each of mass M and radius R are welded symmetrically as shown. The moment of inertia of the arrangement about the axis normal to the plane and passing through the point P is :

Options

A. `(73)/(2)MR^(2)`
B. `(181)/(2)MR^(2)`
C. `(19)/(2)MR^(2)`
D. `(55)/(2)MR^(2)`

Answer

B

Explanation

Moment of inertia about point O
`I_(0)=(MR^(2))/(2)+6[(MR^(2))/(2)+M(2R)^(2)]=(55)/(2)MR^(2)`
Applying || axis theorem
`I_(P)=I_(0)+7m(3R)^(2)=(181)/(2)MR^(2)`