Hamilton’s Principle for the Derivation of Equations of Motion Natalie Baddour nbaddour@uottawa.ca May 30, 2007 Abstract Hamilton’s principle is one of the great achievements of analytical mechanics. It offers a methodical manner of deriving equations motion for many systems, with the additional benefit that appropriate and correct boundary conditions are automatically produced as part of the derivation. It allows insight into the manner that the system is modeled, as any modelling assumptions are clear and the effects of changing basic system properties become apparent and are accounted for in a consistent manner. Simplifications may also be made and Hamilton’s principle can be used as the basis for an approximate solution. Classical mechanics dictates that Hamilton’s principle can only be used for systems that are always composed of the same particles. This has been more recently extended to include systems whose constitutent particles change with time, including open systems of changing mass. In this chapter, we review the principle and its extended version and show through application to examples how it can lead to insightful observations about the system being modelled.
1
Introduction
One of the great accomplishments of analytical mechanics, Hamilton’s variational principle has found use in many disciplines, including optics and quantum mechanics. The development of the equations of mechanics via a variational principle allows the use of powerful approximation techniques for the 1