center of mass

center-of-mass的词性：
n.（名词）

1. The point in a system of bodies at which the mass of the system may be considered to be concentrated and at which external forces may be considered to be applied.Also called barycenter, centroid
质量中心：物体系统上被认为质量集中于此的一点，该点可被认为是外力施加点也作 barycenter， centroid