So the situation is like this a ruler (of uniform mass) is pinned to a nail through its center. The has very little friction so it will spin but come to a stop. Initially it is at rest and is sitting perfectly horizontal (so that means the center of mass is at the center of the ruler). Now I slightly push down on the right end of the ruler with my hand. The main question is, after I release my hand ( no more force) will the ruler return to its horizontal resting place it was initially at or will it just remain at the position where ever the spin stops? This is confusing because when I try this at home with a ruler rotating about my pencil (pencil is through a hole in the middle of my ruler), the ruler always return to some equilibrium position. However, when I think about it, I don't see any other forces that will make the ruler go back horizontally (due to the center of mass being at the center) after I remove my hand that was pushing down. So what is going on here? And what's really suppose to happen with the ruler?