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Objects in a rest position are said to be in equilibrium or we can say balanced between two objects is known as equilibrium. In physics there are many forms of equilibrium like- energy equilibrium, thermal equilibrium, mechanical equilibrium. In this article our main focus is mechanical equilibrium. It is a state in which an object is at rest and is stable as net force acting on an object tends to zero.
Important topics related to equilibrium
Force- a force is a kind of push and pull required to make an object move or stop. Basically it is due to the force that we are able to make an object in motion from its rest position or bring back an object to rest from motion. The SI unit of force is Newton (N).
Net force- it is the total force acting on a body or the combination of all forces acting on an object.
Tension – it is the force which a body suffers when it undergoes stress and strain.
Weight – it is the force of gravity acting on an object in a downward direction.
Vectors – to represent the direction and magnitude of a quantity in physics we use arrows these arrows are known as vectors.
We have two kinds of quantities: vector and scaler.
Vector quantities – quantities having both magnitude and direction are known as vector quantities.
Scalar quantities – quantities which have only magnitude but no direction are known as scalar quantities.
Mechanical equilibrium
A state in which an object is at a rest position that has no physical change occurs. When the net force on an object is zero the object is said to be in mechanical equilibrium position. Mechanical equilibrium can be shown as
ƩF = 0
Where Ʃ shows the total force acting on the body.
Mechanical equilibrium in thermodynamics
When there are no unbalanced forces within or outside a thermodynamic system, it is considered to be in mechanical equilibrium. One such force is pressure. As a result, there should be no pressure gradient in the system. Mutual thermodynamic equilibrium occurs when systems are in mutual thermal, mechanical, chemical and radiative equilibrium at the same time. Some systems are in mutu equilibrium, while others are not. All types of equilibrium hold in thermodynamic equilibrium at the same time and indefinitely until disrupted by a thermodynamic process. The physical rationale for the concept of macroscopic equilibrium is that perfect or almost perfectly balanced microscopic exchanges occur in a macroscopic equilibrium.
There are four types of equilibrium in thermodynamics- mechanical equilibrium, chemical equilibrium, thermal equilibrium, thermodynamic equilibrium.
Support force
The force which acts on an object in upwards direction when an object is at rest is known as support or normal force.
For an object at rest on a horizontal surface, force must equal to the object’s weight.
Equilibrium for moving objects
If the object is not moving it is in equilibrium state and the forces acting on it add up to zero. But the state of rest is not the only form of equilibrium. An object moving in a straight line path with constant speed is also in a state of equilibrium. If there is no net force acting on a body to change the state of motion i.e. body is constantly moving at same speed then it is in equilibrium state.
Basically, equilibrium is a state of no change. Whether an object is at rest or moving with a constant velocity in a straight line path.
Conclusion
To change the object state of motion we need force. When the net force on an object is zero i.e the object is at rest position or moving in a straight line with constant velocity, both are the state of equilibrium. To express equilibrium mathematically- ƩF = 0. If a system does not tend to change, it is said to be in equilibrium. Systems that are in meta- stable equilibrium are those that are in pressure and temperature equilibrium but not chemical equilibrium. For an object at rest on a horizontal surface the force acting on it must be equal to the object’s weight and is known as support force. Objects in rest position are said to be in static equilibrium and objects moving in a straight path with constant speed are said to be in dynamic equilibrium.
