college
posted by Anonymous .
Calculate the force of Earth's gravity on a spacecraft 12,800 km (2 Earth radii) above the Earth's surface if its mass is 1550 kg.

Newton has a neat law of gravity:
Fg= G Me Ms /distance^2
That leads to the inverse relation.
The weight at Earth's surface is mg, which is at one Earth radii.
So if you go one more Earth radii, the weight will be mg/2^2
and if you go one more, as you asked, the weight will be mg/3^2