1. So, during one of my classes, the teacher showed us a small experiment, and asked us to explain how it works. The experimented consisted of a tube, closed on both ends, and attached to said tube is what I think is a magnet. Now, everytime he rotated the tube, the magnet rised to the top with a constant velocity. I held the tube and it felt as if there was a liquid moving inside the tube whilst rotating the tube. Extra: I'm pretty sure the tube was PVC. 3. As I felt a movement, I thought the tube would be filled with a heavy liquid, pushing a magnet on the inside of the tube to the top of the tube when you rotate it, so the liquid must have a higher mass density then the magnet, but this was not it. Any help? Sorry for my english, not my native language..