
Here is a movie from Powerlabs.org
illustrating some concepts of angular momentum. First of all, do not try to repeat
the experiments of Sam Barros. The moment of inertia of a disc of radius L and density rho is I = Pi rho L^{4}/4. If omega is the angular speed (35'000 RPM in the movie), then E=omega^{2} I/2 is the energy of the disc. 
Please send comments to math21a@fas.harvard.edu 
Oliver Knill, Math21a, Multivariable Calculus, Fall 2005, Department of Mathematics, Faculty of Art and Sciences, Harvard University 