Summary

 Kepler's (Three) Laws of Planetary Motion

1. Each planet moves in an elliptical orbit with the Sun at one focus.

2. The line from the Sun to any planet sweeps out equal areas in equal time intervals.

3. For each planet, the square of the period is proportional to the cube of the average radius.

Newton's Law of Universal Gravitation

F_g = G ^{M m}/_d2

Satellite Orbits

F_g = F_c

Low-Earth Orbit

F_g = m g

Geosynchronous Orbit 

T = 24 h