The main difference between the center of mass and the center of gravity is that the center of mass indicates the position where all mass of the object is assumed to be concentrated while the center of gravity indicates the position where all weight of the object is assumed to be concentrated.
Before we look at the differences, let us first understand them.
Contents:
Center of mass:
The center of mass is the point where the whole mass of the object is assumed to be concentrated and its position depends on the distribution of matter into the object which never gets affected by the changes in the gravitational field.
The center of mass is located in the object itself or in some cases it is located outside of the object e.g. center of mass of a solid cylinder is located at its center while the center of mass of the hollow cylinder is located outside of the object in the hollow space.
The whole mass of the object is uniformly distributed around the center of mass. If the body is considered to be made up of ‘n’ number of particles then the sum of the moment of all the particles about the center of mass becomes zero.
Center of gravity:
The Center of gravity is the point at which the whole weight of the object is assumed to be concentrated. The position of the center of gravity depends on the gravitational field acting on the object.
When the gravitational field acts uniformly over the object, then the center of gravity lies at the center of mass of an object.
The non-uniform gravitational field changes the weight distribution of the object and in this case the center of gravity shifts away from the position of the center of mass toward a stronger gravitational field.
Center of mass vs Center of gravity:
| Sr. No. | Center of mass | Center of gravity |
|---|---|---|
| 1 | The point where the whole mass of the body is assumed to be concentrated is known as the center of mass. | The point where the whole weight of the body is assumed to be concentrated is known as the center of gravity. |
| 2 | The gravitational field has no effect on center of mass. | When the gravitational field acting over an object is non-uniform, then the center of gravity moves toward the region of a stronger gravitational field. |
| 3 | The center of mass depends on the distribution of mass over an object. | The center of gravity mainly depends on the nature of gravitational field acting over the object. |
| 4 | The mass of an object is uniformly distributed around the center of mass. | The weight is uniformly distributed around the center of gravity. |
| 5 | The center of mass is denoted by the symbol CM. | It is denoted by the symbol CG. |
| 6 | The center of mass never changes its position. | The center of gravity can change its position due to the non-uniform gravitational field. |
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