"The center of gravity G is a point which locates the resultant weight of a system of particles... To study problems concerning the motion of matter under the influence of force, i.e. dynamics, it is necessary to locate a point called the center of mass..." p435

CENTER OF GRAVITY

CENTER OF MASS

CENTER OF MASS
A POINT WHERE THE MASS OF AN OBJECT SEEMS TO BE CONCENTRATED

CENTROID
A CENTER POINT OF A SHAPE

DIFFERENTIAL ELEMENT
A VERY SMALL ELEMENT OF LENGTH, AREA, MASS, VOLUME, ELECTRIC CHARGE, ...

GRAVITY
THE ATTRACTIVE FORCE BETWEEN ANY TWO MASSES

MASS
THE RESISTANCE OF AN OBJECT TO A CHANGE IN TRANSLATIONAL MOTION