The moment of inertia of a sphere about its diameter is I. Four such spheres are arranged as shown in figure. Find the moment of inertia of the system about the axis XX'. (radius of each sphere is 2R).

Explanation

Unless explicity mentioned any sphere should be assumed to be solid.
`I = 2/5 M(2R)^2`or, `M(2R)^2 = 5/2 I`
`rArr " "I_("system") = I + 2[I + M (2R)^2]+I`
`=I + 2I + 2xx5/2I+I =9I`