If the satellite is to remain over the same point on the Earth, the satellite will have to match the rotation of the Earth on its own axis. This means that the angular velocity of the satellite must equal that of the Earth.
The Earth rotates once around its axis in 24 hours. We need to convert this to radians per second.
The satellite will be held in orbit by the gravitational attraction of the Earth, but we need to find the altitude that the gravitational force provided equals the centripital force necessary to keep the satellite orbiting and not falling into the Earth at the angular velocity we found above. Therefore we set the two equations, the gravitational force and the centripital force, equal to each other and solve for r.
We have to remember to subtract off the radius of the Earth to get the altitude over the surface of the Earth.
