First we’ll finish the remains from the previous class:

- the last part of “Why Mathematics Is So Effective in Physics”, and
- the second half of the lecture on the principle of least action.

Then we’re going to work out some problems in class using the principle of least action, also called Hamilton’s Principle. This will involve correctly setting up the Lagrangian for each problem and working out the equations of motion using the Euler-Lagrange equations. We will work these problems out in detail, omitting little algebra. I’ll try to have hardcopies of this material available at class time.

Then we’ll take up Lecture 7, Symmetries and Conservation Laws. In this lecture Susskind defines symmetries and shows how they lead to the conservation of various quantities. Near the end of the lecture we’ll work on a few problems, just as we did above.

Assignment: **Read Lectures 6 and 7 in the book. If time allows, view Lecture 3.**