What is the difference between centre of mass and centre of gravity?

Asked by  | 19th Dec, 2013, 09:04: PM

Expert Answer:

Center of mass of a rigid body is also called its center of gravity. However, this is true only in circumstances where gravitational forces are uniform. Since gravitational force of earth is taken to be uniform at all places, the center of mass and the center of gravity are effectively same.
Center of gravity is defined as the average location of the weight of an object. In the case of earth, since gravitational pull is same at all places, each mass element would weigh the same so the center of gravity is identical to the center of mass.
However, in a non uniform gravitational field, the center of gravity is not the same as the center of mass. Center of mass is a fixed property which is the average location of the mass of the body. It has nothing to do with gravity.
Consider a situation in which gravitational field is non-uniform. Also, imagine a very long uniform rod.
If you consider two parts of rod with same mass, the force of gravitation (weight) will be different on both instead of same mass. Due to which, its centre of gravity and center of mass will be different.
Because of this, the position of centre of mass of this rod will be different from that of centre of weight.
 

Answered by Faiza Lambe | 20th Dec, 2013, 09:05: AM

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