This calculator will give you the speed that a satellite has to go at in order to maintain earth orbit. Just input the height of the satellite. This assumes no atmosphere, that the earth is a perfect sphere, and that there are no other planetary bodies. DISCLAIMER: NASA, DO NOT USE ANY OF THIS, IF YOU DO, I AM NOT LIABLE FOR ANY DAMAGES.
I did the math by myself, however, I got the idea from "Change is the Only Constant" (Ben Orlin) It is truly an exceptional book, and I would recommend it to anyone who is remotely interested in math.
