#5.4.2a
Newton’s law of gravitation;
\(F = -\dfrac{GMm}{r^2} \) for the force between two point masses
#5.4.2b
gravitational field strength \(g = -\dfrac{GM}{r^2} \) for a point mass
#5.4.2c
gravitational field strength is uniform close to the surface of the Earth and numerically equal to the acceleration of free fall.