F = GMm/r^2

• G = 6.674 x 10^{-11} N*m^2/kg^2 (universal gravitational constant)
• Dimensions of G: [M^{-1}L^3T^{-2}]
• The force is always attractive, acts along the line joining the centres
• Valid for point masses or spherically symmetric bodies (treat as point masses at their centres)
• This is an inverse-square law: doubling the distance reduces force by a factor of 4

Superposition principle: The gravitational force on a body due to multiple masses is the vector sum of individual forces. F_net = F_1 + F_2 + F_3 + ...