Two particles having masses m1 and m2 are situated in a plane perpendicular to line AB at a distance of r1and r2 respectively as shown.
Find the moment of intertia about axis passing through centre of mass and perpendicular to line joining m1 and m2
m1m2m1+m2 (r1+r2)2
Centre of mass of system rcm=m2(r1+r2)(m1+m2) = distance of centre of mass from m1
Distance of centre of mass from mass m2= m1(r1+r2)(m1+m2)
So moment of inertia about its centre of mass I=m1[m2(r1+r2)(m1+m2)]2+m1[m2(r1+r2)(m1+m2)]2=m1m2(r1+r2)2(m1+m2)