A container with helium is sealed by a movable heavy piston as shown. Initially, the piston is in equilibrium. The piston is then slowly lifted a distance L and held until the thermal equilibrium with the surroundings is reestablished. After that, the container is thermally insulated from the surroundings and piston is released. Eventually, it comes to rest. What is the final position of the piston with respect to its initial position? Neglect the outside air pressure on the piston and the heat capacities of the piston and the container.

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The solutions to our November Challenge, Squaring the Circle, came from all over the world—but quite a few of them were incorrect. We are pleased to recognize the following contributors:

André Bellemans (Université Libre de Bruxelles, Belgium)

Philip Blanco (Grossmont College, El Cajon, CA)

Don Easton (Lacombe, Alberta,...

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