Kepler's (Three) Laws of Planetary Motion1. 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 GravitationFg = G M m/d2
Satellite OrbitsFg = Fc
Low-Earth OrbitFg = m g
Geosynchronous OrbitT = 24 h
(C) 2003, Doug Davis; all rights reserved