In physics, a center of gravity of a material body is a point that may be used for a summary description of gravitational interactions.
In a non-uniform field, gravitational effects such as potential energy, force, and torque can no longer be calculated using the center of mass alone.
This line is parallel to the weight F. In general, there is no way to choose a particular point as the unique center of gravity.
[7] A single point may still be chosen in some special cases, such as if the gravitational field is parallel or spherically symmetric.
If the external gravitational field is spherically symmetric, then it is equivalent to the field of a point mass M at the center of symmetry r. In this case, the center of gravity can be defined as the point at which the total force on the body is given by Newton's Law: where G is the gravitational constant and m is the mass of the body.
As long as the total force is nonzero, this equation has a unique solution, and it satisfies the torque requirement.
[12] A convenient feature of this definition is that if the body is itself spherically symmetric, then rcg lies at its center of mass.
[14] When it is necessary to consider a gravitational torque, it is easier to represent gravity as a force acting at the center of mass, plus an orientation-dependent couple.