Can somebody explain to me clearly what is MOMENT OF INERTIA, what is TORQUE, what is ANGULAR MOMENTUM. If you ever comparing those with linear motion quantities, then please explain a little in detail what is the similarity between moment of inertia and mass, as I'm not getting it. Also, I would also request you to answer this question.(it might help): What will happen if I am far out in space in a region without (or negligible) graviatational forces and try to spin a sphere. -Would it spin for ever? (unless I do something) -If it would, then each particle will undergo circular motion, which means that a constant centrifugal force is being applied towards the centre. If so, then who is applying it? -Wouldn't that violate Newton's Second Law? -Would it spin for sometime and then stop (refer Q.1) Any attempt of explanation is appreciated.