<P> In physics, the center of mass of a distribution of mass in space is the unique point where the weighted relative position of the distributed mass sums to zero, or the point where if a force is applied it moves in the direction of the force without rotating . The distribution of mass is balanced around the center of mass and the average of the weighted position coordinates of the distributed mass defines its coordinates . Calculations in mechanics are often simplified when formulated with respect to the center of mass . It is a hypothetical point where entire mass of an object may be assumed to be concentrated to visualise its motion . In other words, the center of mass is the particle equivalent of a given object for application of Newton's laws of motion . </P> <P> In the case of a single rigid body, the center of mass is fixed in relation to the body, and if the body has uniform density, it will be located at the centroid . The center of mass may be located outside the physical body, as is sometimes the case for hollow or open - shaped objects, such as a horseshoe . In the case of a distribution of separate bodies, such as the planets of the Solar System, the center of mass may not correspond to the position of any individual member of the system . </P>

Where is the center of mass of an object