1. Universal Law of Gravitation
Every object attracts every other object with a force that is directly proportional to the product of the masses of the objects and inversely proportional to the square of the distance between them.

2. Calculating Gravitational Force
Fg = gravitational force or weight or force of attraction, N
G = universal constant of gravitation (= 6.67 x Nm2/kg2)
m1, m2 = masses of objects, kg
d = distance from center of one object to center of other object, m Fg Fg m1 m2 d

3. Calculating “g”
Note: m= mass of the object that is being attracted or accelerated (mass that is orbiting about another object)
M = mass of the object that is attracting or accelerating ‘m’ (mass that is being orbited about)
r = radial distance (same as d)

4. Orbital Velocity for a Satellite moving in a Circular Orbit
Centripetal Force = Gravitational Force v

5. Another Formula for Orbital Speed
Fc = Fg
Note: You must know g to use this equation for v!

6. Orbital Period of a Satellite

7. Useful Constants G = 6.67 x 10 -11 N m2/ kg2
Mass of Earth = 5.98 x1024 kg
Radius of Earth = x 106 m
Earth’s orbital radius = 1 A.U.
Earth’s orbital period = 1 year