M-EngMom15: Conservation of energy
 
PIRA: Unknown 

Equipment: A large yellow coffee can located in Set 10, Cabinet 3, Shelf 3.

Procedure: This can contains a hidden weight hanging on a horizontally-stretched rubber band. If you roll the can away from you on a table, it will roll a ways, stop, and then return. This is puzzling behavior, of course. Give the students a little time to think about this, and then point out that when the can was stopped, it must have had some stored potential energy which, on the return trip, was converted to kinetic energy. Then open one end of the can to show its interior and remark that the initial kinetic energy was partially converted to elastic potential energy in the rubber band, and that is the source of the kinetic energy on the trip back.