I spent all of yesrterday going over a set of puzzles. One of them was: Assume you have a container divided into two equal sections (one on the left and one on the right). One section is filled with water and the other with air. A log is placed a long the divider between these two sections using a frictionless axle and frictionless seals (to keep the water out of the air). Does the log spin? (Since one side is falling and the other is floating) (it would like something like this really bad drawing:) Code (Text): Water |Air|---| | o | |___|___| Basic physics (gravity, torque and bouyance) says that the log would spin. But even more basic physics (energy conservation) says it won't. What am I missing? Does it have something to do with the fact that the log won't actually float upwards? Will the log rotate for a short period of time?