Hey everyone, The following question is giving my friend and I a really hard time. My work is shown below. 'what is the total amount of energy needed to place a 2.0 x 10^3 kg satellite in circular Earth orbit, at an altitude of 5.0 x 10^2km above the surface of the earth? Here are all the numbers needed to carry out the problem: M = 5.8 x 10^24 kg (mass of earth) m = 5.0 x 10 3 kg (mass of satellite) r1 = 6.38 x 10^6 m (radius of earth) r2 = 5.0 x 10^5 m + 6.38 x 10^6 m (altitude plus radius of earth) G = 6.67 x 10^-11 N/kg. (Earth's gravitational field strength) I figured that the energy needed would be equal to the energy of the satellite in orbit minus the energy of the satellite on earth's surface....giving thus: E(needed) = -1/2(GMm/r2) - (-GMm/r1) where did I go wrong? Thx!