Interesting mechanics questions

1. Nov 23, 2008

corvus606

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?

2. Nov 23, 2008

Mapes

Hi corvus606, welcome to PF. In these forums it's typical to describe your own solution efforts first, including where you ran into trouble. That way we all see each other's various problem-solving styles. Also, it lets the forum members help you figure out the answer rather than just giving you the answer. So what are your thoughts on the problems?

3. Nov 24, 2008

Naty1

This (entire) question is not worded properly in English...I do not know what you mean...for one thing, did you mean a cylindrical shape (shape of a flagpole) wood rather than spherical (round like a ball??)...

I have no idea what you are asking here. But there is nothing periodic in your example...If the end of the line is left loose a vertical cylinder tie will likely fall of its own weight...