Three rings, each of mass `m` and radius `r`, are so placed that they touch each other. Find the moment of inertia about the axis as shown in Fig.

Options

A. `5mr^(2)`
B. `5/7mr^(2)`
C. `7mr^(2)`
D. `7/2mr^(2)`

Answer

D

Explanation

`I=I_(1)+I_(2)+I_(3)`
`I_(1)=I_(2) =3/2mr^(2)`

`I_(1)=I_(2)=3/2mr^(2)`
`I=I_(1)+I_(2)+I_(3)=7/2mr^(2)`