Three rings, each of mass P and radius Q are arranged as shown in the figure. The moment of inertia of the arrangement about YY' axis will be

Options

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

Answer

A

Explanation

`I_(d)=(1)/(2)mR^(2)`.
We have
`I=I_(1)+I_(2)+I_(3)`
`=((1)/(2)mR^(2)+mR^(2))+((1)/(2)mR^(2)+mR^(2))+(1)/(2)mR^(2)`
`(7)/(2)mR^(2)`