this is quoted from feynman's "surely youre joking, mr. feynman" "i once did an experiment in the cyclotron lab at princeton that had some startling results. there was a problem in a hydrodynamics book that was being discussed by all the physics students. the problem was this: you have an S-shaped lawn sprinkler- and S-shaped pipe on a pivot- and the water squirts out at right angles to the axis and makes it spin in a certain direction.everyone knows which way it goes around; it backs away from the outgoing water. now the question is this: if you had a lake, or a swimming pool-a big supply of water- and you put the sprinkler completely under water, and sucked the water in, instead of squirting it out, which way would it turn?" so, which way would it spin?