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Overview
The center of mass is the average location of mass in an object or system. It is the point where the mass distribution can often be treated as concentrated for analyzing overall translational motion.
Mass Distribution
Mass distribution describes how matter is spread through an object or system. If more mass lies on one side, the center of mass shifts toward that side.
Systems of Objects
A system of multiple objects has a center of mass determined by the positions and masses of all objects in the system.
Motion of the Center of Mass
The center of mass of a system moves as if the total external force acts on the total mass located at that point.
Balance and Stability
An object is more stable when its center of mass is low and located above its base of support.
Center of Mass in Projectile Motion
A thrown object may spin or tumble, but its center of mass can follow a simple projectile path when air resistance is ignored.
Center of Mass in Collisions
In collision problems, center-of-mass motion connects directly to total momentum conservation.
Center of Mass and Center of Gravity
Near Earth’s surface, center of mass and center of gravity are often treated as the same point because gravity is nearly uniform.
Common Mistakes
A common mistake is assuming the center of mass must lie inside the material of an object. Another is assuming the geometric center is always the center of mass.
Why This Matters in Physics
Center of mass connects motion, balance, stability, collisions, rotation, and systems thinking.