A space craft of mass 5.9×104 kg is in orbit around a planet of 5.1×1024 kg. If the planet can be assumed to be a uniform sphere of radius 5.4×106 m and the space ship is orbit a height of 6.9×105 m above the surface what is the gravitational potential energy of the ship? [G=6.674×10-11 Nm2kg-2]
[Specify units of 'J', 'kJ', 'MJ' or 'GJ' in your answer.]
so far what I have done is used the equation for GPE
U = - (G me m) / r
where G is 6.674e-11 Nmkg-2
me is the mass of the planet 5.1e24 kg
m is the mass of the space ship 5.9e4 kg
r is (i think) the radius of the planet (5.4e4 m) added to the height of the space ship is above the planet (6.9e5 m) and then divided it into G me m
but still I dont get the right answer.......
where am I going wrong?