The following question deals with planetary motion: energy totals and binding energy. I have solved the question to the best of my ability, but I cannot get the right answer! I don't know what I am doing wrong, and would greatly appreciate it if someone could point out my mistakes. 1. The problem statement, all variables and given/known data This is a two part question. 1. a) What is the total amount of energy needed to place a 2000 kg satellite in circular Earth orbit, at an altitude of 500km? b) How much additional energy would have to be supplied to the satellite once it was in orbit, to allow it to escape from the Earth's gravitational field? 2. Relevant equations a) Etot = 1/2 Eg Etot = 1/2 -(GMm)/d b) Etot > Eg 3. The attempt at a solution a) m = 2000 kg M = mass of Earth = 5.98x10^24 kg d = 500 000 m + 6.38x10^6 (radius of earth) d = 6.88x10^6 m Etot = 1/2 Eg Etot = 1/2 -(GMm)/d Etot = 1/2 -(6.67x10^-11)(5.98x10^24)(2000)/6.88x10^6 Etot = - 6.0x10^7 J However - the correct answer is 6.7x10^7. That seems like a big difference - does anyone know what I am doing wrong? b) I know I am being asked for the binding energy - the extra amount of energy required to break free of the gravitational field of the earth, also known as Etot. My total energy is - 6.0x10^7 J, so I assume I would need + 6.0x10^7 J to overcome it. However - the correct answer is 5.8-x10^10 J. Please point me in the right direction if you can.