1 Euler’s laws and Lagrange’s equations by applications Bulletin de l’Union des Physiciens Tiberius O. Cheche*, Ecaterina O. Cheche** University of Bucharest, Faculty of Physics, Department of Polymers Physics P.O.Box 5211-Magurele R-76900, Bucharest **High School “Jean Monnet”, Bucharest ROMANIA Phone number: 40-1-3309873 Fax number: 40-1-4208625 E-mail: cheche@digi.ro * the author to whom the correspondence should be addressed Abstract: The Euler’s laws and Lagrange’s equations are shortly presented in a directly applicable form to a problem of classical mechanics. The proposed problem offers a didactical tool to observe how the equations of the plane motion of a rigid body could be applied and understood from the perspective of Newton and Lagrange mechanics. For simulation of the proposed motion some concrete calculus are presented. 1. Introduction In its chronological evolution the classical mechanics has known three fundamental formulations, those of Newton, Lagrange and Hamilton. D’Alembert‘s principle and the Published by Bulletin de l'Union des Physiciens (France), Vol. 96, p. 83, 2002