WHAT IS CENTRE OF GRAVITY AND CENTROID OF A BODY?

Centre of gravity

Centre of gravity of a body is defined as the point through which the whole weight of the body acts. A body can have only one centre of
gravity for all positions of the body. It is represented or denoted by C.G. or G.

Centroid

The point, at which the total area of a plane figure (such as rectangle, triangle, square, quadrilateral, circle etc) is assumed to be concentrated, is called the centroid of that area. The centroid is also represented by C.G. or G.The centroid and centre of gravity are at the same point. 

Centroid or centre of gravity of simple plane figures:

• The C.G. of a uniform rod lies at its middle point.

• The C.G. of a triangle lies at the point where all the three medians intersect each other.

• The C.G. of a rectangle (or a parallelogram or a square) lies at the point where its diagonals intersect each other. It is also the point of intersection of the middle points of the opposite sides.

• The C.G. of a circle lies at its centre.