JEE Main | 2018Rotational MotionHard

Question

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.

552MR2

B.

732MR2

C.

1812MR2

D.

192MR2

Solution


I0 = Icm + md2
=7MR22+ 6(M×(2R)2) = 55MR22
Ip = I0 + md2 
=55MR22+7M (3R)2=1812MR2

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