Centre of mass is the definition. Another definition for centroid that Ive seen is Centre of mass. Equation For Center Of Mass Video Khan Academy Centre_of_mass centre_of_mass Point representing the mean position of the matter in a body. . For example the gravitational force on Earth attracts small objects as if it were pulling them from their center of mass in this case the. In the case of a system of particles Pi i 1n each with mass mi that are located in space with coordinates ri i 1n the coordinates R of the center of mass satisfy the condition. The centroid is the geometrical centre of an object. The centre of mass is the weighted average of the locations of the masses so if one of the objects is more massive the centre of mass will be closer to the more massive object. The centre of mass of the system is defined as the point O_1 with position vector vecR is given by vecRdisplaystylefracm_1vecr_1m_2vecr_2cdotsm_nvecr_