Author's Homepage:   R. C. Hibbeler
Chapter 9: Center of Gravity and Centroid
"Center of Gravity. The center of gravity G is a point which locates the resultant weight of a system of particles. To show how to determine this point consider the system of n particles fixed within a region of space as shown in Fig. 9-1a. The weights of the particles comprise a system of parallel forces which can be replaced by a single (equivalent) resultant weight having the defined point F of application. To find the xbar, ybar, zbar coordinates of G, we must use the principles outlined in Sec. 4.9."