Question

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 1300 kg

FG =		N

Answer 1

F= Gm1m2/r^2
Given:-
distance (r) = 12800 km = 12 800 000 m
mass of spacecraft (m1) = 1300 kg

Then we need to know a bit about the mass of the Earth and the value of G (the Gravitational constant)
mass of Earth (m2) = 5.9742 x 10^24 kg
gravitational constant (G) = 6.674 x 10^-11 Nm^2/kg^2
Then we substitute the values,
F =6.67 x 10^-11 x 5.9742 x 10^24 x 1300/12800000^2
F =51802.2882×10^9 / 16384 × 10^10
F = 3161.760N