For a circular orbit, the force of gravity must equal the centripetal force on the satellite.
[tex] \frac{GmM}{R^2} = m \frac{v^2}{R} [/tex]
G gravitational constant
M mass of earth
m mass of satellite
R radius of orbit
the mass m cancels:
[tex]v = \sqrt{\frac{GM}{R}} [/tex]
