Q. Explain the terms centre of gravity and centroid.

Sol.: A point can be found out in a body through which resultant of all such parallel forces acts. This point through which whole weight of body acts irrespective of position of body is called as centre of gravity. Everybody has one centre of gravity.

The plane figures like rectangle, circle, triangle etc., have only areas, but do not have mass. The centre of area of such figure is called as centroid.

The method of finding centroid of a figure is same as that of finding out C.G. of body.

X =     Ai . xi/A

Y =  Ai . yi/A

C.G. = (X,Y)