A person weighing 800 newtons travels to another planet with twice the mass and twice the radius of earth. what is the person's weight on the new plant?

F=m1*m2*G/r2. m1 anf m2 are the masses. G is the universal gravitation constant (=6.673*10^-11). R is distance between m1 and m2. So the earth's mass is 5.98*10^24 kg, m1, person is 800 / 9.81=81.55 kg. Now all we have to do is film in: F = 6.673*10^-11*81.55 kg * (5.98*10^24 * 2kg) / (6.38*10^6*2) ^2 = 399.73 N. You may recalculate, maybe I forgot something, but the formula is right.

1600 Newton

800*2 = 1600