A space rocket of mass 1500kg travelled from the Earth to the Moon, a distance of 3.8 x 10^8 m.
When the space rocket was mid-way between the Earth and the Moon, calculate the force of gravitational attraction on it due to the Earth.
I used F = GMm/r^2 with r = distance from Earth to Moon/2 + radius of Earth and got 15 N. Textbook however says answer is 16.6 N. Was I not supposed to include the radius of the Earth in the calculation and if so, why not?