OK, this is not a homework problem, I was simply fooling around when I conjured this up. And I guess I must include that I'm only a beginner to physics so my knowledge is limited. Now, for the questions. Say there is a hollow massless rod, and inside it you have a ball of certain mass, the radius of the ball is equal to that of the rod and there is no friction between the two surfaces. Now if I were to keep it on a table and give it a spin, will the ball remain in centre or stick to one of the ends of the rod? My intuition tells me it would stick to one end but I'm not 100℅ sure about it. OK, now for the real one, now consider the same rod and throw it keeping it vertically in such a way it does a combined rotational and translational motion, does the ball keep going up and down as the rod spins? Or again, does it stick to one end? I'll again guess here that if I give it a certain angular velocity such that the centrifugal force overcomes the gravitational force, it would stick to one end (keep in mind that I have assumed the ball to be in one of the ends when the motion is just about to begin, does it change if the ball is at the centre when the motion is just about to begin?) Assuming my guess to be correct, say I give it an angular velocity that is not enough to overcome gravitational force, I assume the ball keeps moving from one end to the other as the rod rotates, so essentially, the centre of mass is... Oscillating?... Anyway, What would be the motion described by the body in such a case? And if my guess is wrong, how would the motion be? I know that I have posed quite a few questions but I would be very grateful if I could get the answers for them. Thank you.