For a body in a circular orbit around Earth of radius r, the ratio of kinetic energy to total mechanical energy is

1. For a circular orbit: KE = (1/2) m v² = G M m / (2 r). 2. PE = −G M m / r; total energy E = KE + PE = −G M m / (2 r). 3. Compare: KE = −E, so KE / E = −1, or equivalently 1 : (−1). 4. This is the standard virial-theorem relation for gravitational orbits. _Source: syllabus Physics, Ch 7 "Gravitation", §7.7_