Ok lets see. Did every try to solve this Q or just shoot anserws by reading it?
:P
ok, lets calculate
:
For mass 100kg : the answer is 3.987300564e12
For mass 1kg : the anser is 3.987300564e10
Hence we can say, for small masses we can safely assume the Force to be equal. But for masses greater then about 3/4th of earths we can take it in consideration (This is mine hypothesis...dont know for sure when we take smaller mass in calculations)
Good Q though Biggie 