Question
Four solid rigid balls each of mass m and radius r are fixed on a rigid ring of radius 2r and mass 2m.The system is whirled about ‘O’. The radius of gyration of the system is 128 mr2/30. How???
Joshi sir comment
about O
M. I. of ring = 2m(2r)2
M. I. of one ball = 2mr2/5 + m(2r)2 = 22mr2/5
so total = 8mr2 + 4*22mr2/5
solve
One other thing is that the question is wrong, in the place of radius of gyration, you should write moment of inertia