Question

Which one of the following statements related to center of gravity is incorrect?
A. The center of gravity of an object is defined as the point through which its whole weight appears to act.
B. The center of gravity is sometimes confused with the center of mass.
C. The center of gravity always lies inside the object.
D. For an object placed in a uniform gravitational field, the center of gravity coincides with the center of mass.

Answer 1

In order to answer this question, to choose the incorrect option regarding the center of gravity, we will write the option which is incorrect and then we will also explain the reason behind it. And then we will discuss more about the center of gravity.

Complete answer:
The center of gravity always lies inside the object. The above sentence is incorrect regarding the center of gravity. As it's not necessary that the center of gravity always lies inside the object. It can be outside the object.The centre of gravity lies at the geometric centre of some bodies, such as hollow bodies, frames, and rings, where the object's mass is not present.

The geometric centre of a body, especially in a symmetrically structured object made of homogeneous material, may correspond with the location of the body's centre of gravity.However, an asymmetrical item made up of a range of materials with varying masses is likely to have a centre of gravity that is offset from its geometric centre.

The centre of gravity (or centre of mass) may occur in space at a place exterior to the physical substance in some circumstances, such as hollow bodies or irregularly shaped objects—for example, at the centre of a tennis ball or between the legs of a chair.

Hence, the correct option is C.

Note: In a uniform gravitational field, the centre of gravity is the same as the centre of mass, as physicists prefer to call it. However, the two do not always coincide. The Moon's centre of mass, for example, is extremely close to its geometric centre (though not exactly since the Moon isn't a perfect uniform sphere), yet its centre of gravity is somewhat shifted toward Earth due to the larger gravitational attraction on the Moon's near side.