Two uniform circular discs, each of mass 1 kg and radius 20 cm, are kept in contact about the tangent passing through the point of contact. Find the moment of inertia of the system about the tangent passing through the point of contact.

Explanation

Mass of disc = M = 1 kg.
Radius of disc = 20 cm = 0.2 m

They are in contact as shown.
M.O.I of a circular disc about a tangent parallel to its plane `=5/4 MR^2`
Total M.O.I of the system
`I = 5/4 MR^2 + 5/4 MR^2 = 5/2 MR^2`
`therefore I = 5/2 xx 1 x 0.2 xx 0.2xx 5 xx 1 xx 0.1 xx 0.2`
`= 0.1 kgm^2`