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Code Number: 1J20.10
Demo Title: Stable, Unstable, and Neutral Equilibrium
Condition: Excellent
Principle: Stable, Neutral, and Unstable Equilibrium
Area of Study: Mechanics
Equipment:
Cone, Plexiglas Bowl, Bowling Ball, Inverted Curved Block, Ball with Offset Center of Mass, and Maxwell's Tops.
Procedure:
Place the bowling ball on the table an observe it has a stable equilibrium. This will also be the case when it is in the bowl. However, if you turn the bowl over and try to balance the bowling ball on the top the ball will always roll of as that is an unstable configuration.
The cone can be set on its side or on it base and it will be in a stable configuration. It will be an unstable configuration if you try to balance the cone on its point.
The ball with the offset center of mass will balance on the inverted curved block. A ball with the mass distributed as usual will not.
Maxwell's tops are a good demonstration. The top with the rotation point up in the center will be stable on the rod, whether it is spinning or not. The top with the rotation point extending below the top will not balance on the rod unless it is spinning.
References:
- George D. Freier, "The Tippy-Top", A Potpourri of Physics Teaching Ideas, p. 56.
- Tik L. Liem, "The Plate Carousel", Invitations to Science Inquiry - Supplement to 1st and 2nd Ed. p. 100.
- Julius Sumner Miller, Q131 & A131, Millergrams II – Some More Enchanting Questions for Enquiring Minds, p. 20 & 82.
- Julius Sumner Miller, Q203 & A203, Millergrams II – Some More Enchanting Questions for Enquiring Minds, p. 59 & 109.