I've ecountered three interesting problems lately: 1. On a motionless sphere you can lay a cylinder. In what conndtions it is possible? After we move cylinder by a little degree it starts to vibrate and after a short period of time it goes back to the static situation. Why? 2. When mooring (hope I use a good word ;)) a ship you only need to wrap a line around a spherical wood piece 2-3 times and after that you should have a loose not moving end of a line left. The question was how does the fricition behave in dependence from degree. Is it periodic? 3. When a drop of water is put on a very hot electric burner it starts to move around without evaporating but when the burner is a little bit colder water evaporates momentally. Why?