In the equilibrium of bodies, if the supports are removed and replaced by the supportive reactions then the free body diagram can be understood. Consider the figure below:
Here if the supportive surface is substituted with the reaction RA then that is an example of free body diagram.
- The point of application of the reaction RA will be the point of contact A, and from the law of equilibrium of two forces.
- We will concentrate upon that the reaction RA must vertical and equal to the weight W.
- Hence Fig.2.1 (c), in which the ball is completely isolated from its support and in which all forces acting on the ball are shown by vectors, is known a free-body diagram.