In a stationary body, some external forces are acts the body may start or moving or rotating about any point. But if the body does not start moving and also does not start rotating about any point is known as "Equilibrium".
The principle of equilibrium states that,a stationary body which is subjected to coplanar forces will be
in equilibrium if the algebraic sum of all the external forces is zero. The algebraic sum of moments zero of all the external forces about any point in their plane.
It can be expressed
∑F = 0
∑M =0
Equation of Equilibrium for Non Concurrent Forces Systems
Equation of Equilibrium for Concurrent Forces Systems
The principle of equilibrium states that,a stationary body which is subjected to coplanar forces will be
in equilibrium if the algebraic sum of all the external forces is zero. The algebraic sum of moments zero of all the external forces about any point in their plane.
It can be expressed
∑F = 0
∑M =0
Equation of Equilibrium for Non Concurrent Forces Systems
A Non Concurrent force systems will be in equilibrium if the resultant of all forces and moment is zero.
The equations of equilibrium are
∑Fx
= 0 ,∑Fy = 0 and ∑M =0
Equation of Equilibrium for Concurrent Forces Systems
For the Concurrent forces,the lines of action of all forces meet at a point, and hence the moment of that force about very point will be zero. ∑M =0 becomes zero.
Types of Forces on Body
Types of Forces on Body
Applying equilibrium conditions to a body it is essential that all forces acting on the body should be considered.The various forces acting on a body
1. Applied forces
These forces applied externally to a body.Each force got a point of contact with the body.
2. Non-applied forces
Two types of Non-applied forces are
a) Self-weight : Self-weight acts in vertically downward direction.
b) Reactions : These are self adjusting forces. The reactions adjust themselves to bring the body
to equilibrium.
FREE BODY DIAGRAM
Applied forces, self-weight and the reactions at the points of contact with other bodies are dawn. Such a diagram of the body in which the body under consideration is freed from all the contact surfaces and all the forces and all the forces acting on it are drawn, is called a "Free Body Diagram".
MOMENT OF A FORCE
It is the product of a force and perpendicular distance of the line of action of the force from a point.
Let,
F= A force acting on body
r= Perpendicular distance from the point O on the line of action while force apply.
Then Moment is
M= F x r
Applied forces, self-weight and the reactions at the points of contact with other bodies are dawn. Such a diagram of the body in which the body under consideration is freed from all the contact surfaces and all the forces and all the forces acting on it are drawn, is called a "Free Body Diagram".
MOMENT OF A FORCE
It is the product of a force and perpendicular distance of the line of action of the force from a point.
Let,
F= A force acting on body
r= Perpendicular distance from the point O on the line of action while force apply.
Then Moment is
M= F x r
Moment in Clock-wise direction -ve
Moment in Anti Clock-wise direction +ve
Moment in Anti Clock-wise direction +ve