Dynamics 8 12-1 The center of mass of a system of particles, external forces and internal forces 1. The center of mass The center of mass of a system of particles is called center of mass. It is an important concept representing the distribution of mass in any system of particles The position of the center of mass c is (M=>m) ∑m OrMC示 ∑ From r=x i+y+=k, we got ∑mx ∑m ∑m M9 1. The center of mass. The center of mass of a system of particles is called center of mass. It is an important concept representing the distribution of mass in any system of particles. §12-1 The center of mass of a system of particles, external forces and internal forces ( =  ) M mi  =  C = i i i i C Mr m r M m r r or From r x i y j z k ,we got c = c + c + c M m z z M m y y M m x x i i C i i C i i C    = , = , = The position of the center of mass c is