In the book Surely You’re Joking Mr. Feynman Feynman describes a problem involving an S shaped lawn sprinkler.
This is the problem. The S shaped lawn sprinkler has holes drilled at a right angle to the axis. When you turn on the water the sprinkler turns away from the stream of water. For example, if the S shape is laid in front of you the S will turn in the clockwise direction. Now the question is, which way will the sprinkler turn if it sucked in water instead of pushing it out.
Fenyman gives arguements for the sprinkler turning both ways. In the book he states that he tried an experiment in a carboy to figure out what would happen and he figured out which way it would go. He then describes the carboy blowing up and getting a lecture from a Professor about how Freshman experiments should be done in the Freshman lab. But he never states which way it turns.
This is driving me nuts and I don’t have the equipment to try it myself.
Help, please. (I think it turns in the same direction. Well, at least today I do)
…not that I have a cite for this or anything, but I had a professor in college who was talking about this particular experiment from Fenyman’s book. He and some fellow professors couldn’t decide which way the damn sprinkler would work either, so they designed a sprinkler, followed the setup described in the book, and…
…well, the thing didn’t really do much of anything. Lets hear it for science.
A professor at George Mason U named Robert Ehrlich (no, not the new governor of Maryland) designed a simple demonstratiion that you can make at home. Take a soda can and cut four small tabs near the bottom so that the tabs can be bent inward at an angle. Attach a lead weigt to the bottom of the can, enough to make it sink when you put it in water. Punch two small holes on opposite sides near the top, and tie a thread through them. Tie another thread to this thread, so that the can spins around when you hold the thread. Now lower the can into water. This is the “inverse sprinkler”. When you pull the can back out, the water runs out: the regular sprinkler. They rotate in opposite directions. As predicted.
