DAVID G. SIMPSON 


LEES' RULELees' rule is a formula for computing the moment of inertia of a symmetrical solid. It is really a kind of mnemonic device for helping to recall several moment of inertia formulae. Lees' rule states that the moment of inertia I of a body of mass M about an axis is given by^{[1]}where a and b are the lengths of the semiaxes perpendicular to the rotation axis, and n and n' are the "numbers of principal curvature" that terminate semiaxes a and b, respectively (n, n' = 0 for a flat surface, 1 for a cylindrical surface, or 2 for a spherical surface). ExampleFor example, suppose we want to find the the moment of inertia of a rectangular plate of dimensions ℓ × w, about an axis through the center of the plate and perpendicular to the plane of the plate. Then a = ℓ/2, b = w/2, and n = n' = 0 because the surfaces are flat. Then Lees' rule givesSee AlsoReferences^{[1]} H.J. Gray and A. Isaacs (eds.). A New Dictionary of Physics. Longman, London, 1975.Contact InformationI may be contacted at: 
Copyright © 2006 David G. Simpson
http://www.DavidGSimpson.com