I am not too sure where to post this, but i suspect that it is mechanical so here goes... Not too long ago, i read a book about by Richard Feynman and came upon this puzzle. If you twist a metal tube to form a 'S' shape, then pivot the tube in the center. Next connect a water hose to the center of the tube. The momentum of the water spurting out from both ends of the tube will make the tube spin around like a sprinkler, with me so far? Alright, now the question comes. What if you use the exact same set up, but immerse everything into water. Instead of the water hose, put another hose which leads to a pump, so it sucks in water from both ends of the 'S' tube. Now, how will the tube spin. Will it spin the opposite direction as the first set up, or will in spin in the same direction. Feynman proposed really convincing answers for both options but i forgot what are they and what is the final answer. Anyone ??