Centre of Mass:

The centre of mass (/gravity) of a body or a system of particles is the resultant of the weights of the individual particles making up the body or system. The center of mass of a body or a system of bodies is the point that moves as though all of the mass were concentrated there and all external forces were applied there.

Uniform Bodies

A uniform body is a body whose density is the same throughout the body. Finding the centre of mass of uniform bodies is relatively straightforward.

A lamina is a 2-dimensional object. In other words, it is a flat object whose thickness is we can ignore.

If a body has a line of symmetry, the centre of mass will lie on this line. This fact is very useful. The center of mass of a body does not generally coincide with its geometric center, and this property can be exploited. Engineers try to design a sports car's center of mass as low as possible to make the car handle better. For example, the centre of mass of a circular lamina is at the centre of the circle, since the centre of mass is on each axis of symmetry and they all meet at the centre. Our study of motion has been limited up to this point. We referred particle, object and body in one and same way. We considered that actual three dimensional rigid bodies moved such that all constituent particles had same motion i.e. same trajectory, velocity and accelerationThe term center of mass is often used interchangeably with center of gravity, but they are physically different concepts. They happen to coincide in a uniform gravitational field, but where gravity is not uniform; center of gravity refers to the mean location of the gravitational force acting on a body