A thin circular disk is in the xy plane as shown in the figure. The ratio of its moment of inertia about z and z' axes will be :

Options

A. `1:4`
B. `1:5`
C. `1:3`
D. `1:2`

Answer

C

Explanation

Moment of inertia about axis of disc can be written as follows:
`I_(z)=(mR^(2))/(2)`
From parallel axis theorem
`I_(z)=(1)/(2)mR^(2)+mR^(2)=(3)/(2)mR^(2)`
`(I_(z))/(I_(z.))=(1)/(3)`
Hence option (c) is correct.