Page 43 - eEISBN FINALIZE

CHAPTER 3

EQUILIBRIUM

3.1 INTRODUCTION TO EQUILIBRIUM

This topic discusses the concept and analysis of equilibrium of particles in coplanar system.

Definition : a particle is said to be in equilibrium if sum of all the forces acting on it is equal to
zero

CONDITION FOR EQUILIBRIUM OF PARTICLE

i.Is at rest and remains at rest
ii.Constant velocity if originally in motion

3.2 EQUILIBRIUM EQUATION

According to Newton First Law – A particle originally at rest, or moving in a straight line with
constant velocity, will remain in this state provided the particle is not subjected to an unbalanced

force.
So sufficient condition for equilibrium of particles is

 F = 0 ,  F - sum of all the forces acting on particle

 F = , 0  F x - sum of all the forces acting on particle on x axis
x
 F = , 0  F Y - sum of all the forces acting on particle on Y axis
Y

3.3 FREE BODY DIAGRAM

A diagram showing the particle under consideration and all the forces acting on this particle

This diagram is simply a sketch which shows the particle ‘free’ from its surrounding with all the
forces acting on it

Steps to draw free body diagram:
i. Draw Outline Shape

Imagine that the particle is cut free from its surroundings or isolated by drawing the
outline shape of the particle only

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