PURPOSE: To illustrate stable and unstable equilibrium in a surprising way.
DESCRIPTION: The tilted cylinder at the left topples when the top is added, the classical toppling tower demonstration. The vertical cylinder in the center topples when the top is removed, due to the presence of two heavy balls in the hollow cylinder. The tilted cylinder at the right topples when the top is removed and replaced, due to a weighted top which is rotated when it is replaced. Note that all three cylinders are constructed from the same tubing, and that none has a bottom.
SUGGESTIONS: Have the students figure out why these devices work. You might have your students calculate the conditions under which the center cylinder is unstable when the top is removed.
REFERENCES: (PIRA 1J11.11)
EQUIPMENT: Three toppling cylinders, as photographed.
SETUP TIME: None.
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