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Two thin discs each of mass M and radius...

Two thin discs each of mass `M` and radius `r` are attached as shown in figure, to from a rigid body. The rotational inertia of this body about an axis perpendicular to the plane of disc `B` and passing through its centre is :
.

A

`2M r^(2)`

B

`3Mr^(2)`

C

`4Mr^(2)`

D

`5Mr^(2)`

Text Solution

Verified by Experts

The correct Answer is:
D
`I_(B) = 1/2 mr^(2),I_(A)` about the given axis (by parallel axis theorem) `=1/2 mr^(2) + m(2r)^(2) = 9/2 mr^(2)`
`rArr I=1/2mr^(2)+ 9/2 mr^(2) = 5mr^(2)`
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