In this two-part lesson, Newton’s calculation is applied to artificial Earth satellites. It is shown that, at least for circular orbits, this calculation leads to Kepler’s 3rd law. In addition, the velocity required for a low Earth orbit is derived, and a practical formula is obtained for the orbital period in a circular Earth orbit of any radius. The student will be able to derive the velocity in a circular orbit of any radius, to derive the Earth escape velocity, and to prove Kepler’s 3rd law for circular orbits. The student will also learn a simple formula for the orbital period in a circular Earth orbit of given radius.