Local “reversal of gravity” can be simulated with an inverted pendulum whose pivot is made to oscillate vertically. A beautiful demonstration of this surprising effect can be found in Ref. 1. In this case, the pendulum is a piece of plastic straw and its pivot pin is fixed at the end of a plastic ruler that is made to oscillate vertically by a small eccentric motor. A theoretical treatment of this inverted pendulum may be found in Ref. 2.
REFERENCES
1.
N. A. Downie, Vacuum Bazookas, Electric Rainbow Jelly and 27 Other Saturday Science Projects (Princeton University Press, Princeton, NJ, 2001), pp. 21–27.
2.
Michael J.
Moloney
, “The gravity-defying pendulum
,” Phys. Teach.
40
, 356
(Sept. 2002
).
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© 2005 American Association of Physics Teachers.
2005
American Association of Physics Teachers
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