We show that the time it takes a magnet to fall through a nonmagnetic metallic tube may be found via dimensional analysis. The simple analysis makes this classic demonstration of Lenz’s law accessible qualitatively and quantitatively to students with little knowledge of electromagnetism and only elementary knowledge of calculus. The analysis provides a new example of the power and limitations of dimensional analysis.
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There is a boundary layer in time in this problem. The inertial effect may be recovered by a boundary layer analysis. Alternately, the equation for may be solved exactly.
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© 2005 American Association of Physics Teachers.
2005
American Association of Physics Teachers
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