Class 5, 1/22/04,  Summary

* Reiterate some items related to HW1 and Class 4:
R1. ly/yr =c.
R2. Energy of a particle (in a free space without forces) has two parts: one part is from its rest (intrinsic, or  invariant) mass and another from its speed. Einstein's special reletivity elegantly combine the two together into one term, which we must use when the speed of any object with rest mass becomes non-negligible comparing to c.
(It was pointed out that this discussion was relevant for HW3, SA3.3.)
R3. Four laws of thermodynamics and their implications.

* Started the new material, Chapter 5.
Newton was the first to discover the precise mathematical description of planetary motions, as well as motions of objects on earth.
N1. Newton's Three Laws
N2. Newton's Universal Law of Gravity and derived the g formula. (It was pointed out that similar calculation can be made the g on the surface of Mars, HW3, SA3.4.)
N3. Pointed out the important items to study in TB1: Angular momentum, escaping velocity, and Kepler's third law.