Hi friends the problem is as: https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-ash4/1379445_1440214886205617_1276077735_n.jpg While finding moment of inertia of the system about the point from where the rod is fixed, the book says that M.I. of the system will be, I = Irod + Idisc I = [1/3m(2R)2] + [m(2R)2]-----------(1) Sorry in the figure the length of the rod is 2R. But I think that it should be I = Irod + Idisc I = [1/3m(2R)2] + [1/2m(R)2 + m(2R)2] - - - -- - (2) (Using parallel axis theorem) Please friends tell why it is so? While the (2)nd M.I. which I got, the book says that it will be for, https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-ash4/q71/1378467_1440214882872284_972543142_n.jpg Please friend help me in this confusion. I will appreciate the help. Thank you all in advance.