F = $\frac{GMm}{r}$^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. $F_{net}$ = $F_1$ + $F_2$ + $F_3$ + ...