Lecture 3

Figure 3.2 - Polar coordinates

We first define action and its relationship to the Lagrangian of a mechanical system.

We then introduce the principle of least action - a very general and powerful principle of physics, which, although equivalent to Newton's Law, can be applied in contexts where it would be immensely difficult to use Newton's Law.

We then apply the formalism to free particles and take a first look at the main subject of the course - the relationship between conservation laws and symmetries of the system.