Dynamic equilibrium vs Static equilibrium: Comparative Analysis

This article discusses about dynamic equilibrium vs static equilibrium. That is the major differences between them.

If the reader is not aware about the meaning of both these terms, he/she need not worry as this article discusses about definition, examples as well as the differences between dynamic equilibrium and static equilibrium.

Dynamic equilibrium vs static equilibrium

Although, in dynamic equilibrium the contents inside the system may seem to be still or at rest but in actual the contents are continuously moving. In static equilibrium, the contents are actually at rest.

The differences between dynamic and static equilibrium are given below-

Dynamic EquilibriumStatic equilibriumThe nature of this equilibrium is reversible.The nature of this equilibrium is irreversible that is it cannot go back to the same state without interference of external factors.
Both the reactants and products are active participants in the reaction.The reaction stops and no further reaction takes place.
The forward and backward reactions are equal.The forward and backward reactions rate in static equilibrium are zero as everything is in static condition.
 It cannot occur in open systems. It can occur only in closed systems.Static equilibrium can occur in both open and closed systems.
Table: Difference between static equilibrium and dynamic equilibrium

What is dynamic equilibrium?

Equilibrium relates to stability. The word dynamic means something which is in motion and dynamic equilibrium relates to equilibrium of bodies in motion.

When the body is in dynamic equilibrium, the rates at which the forces are acting are equal and opposite in nature such that the net sum of these forces is constant or zero. In chemistry, the rates at which the reactants and products are used and formed are equal that is the forward reaction to backward reaction.

Image credits: Wikipedia

What is static equilibrium?

Statics relates to bodies that are at rest. Static equilibrium is the equilibrium of bodies that are at rest (not moving).

When the body is in static equilibrium, the sum of forces acting on the body will become zero. The forces act in such a way that the body does not displace from its original position.

Examples of dynamic equilibrium

Dynamic equilibrium can be observed in our daily lives. Lets see some examples of dynamic equilibrium that we observe in day to day lives-

  • A reversible chemical reaction- The reaction in which rates of forward reaction and backward reaction are equal.
  • A new bottle of soda bottle- The Co2 present inside the soda can is in dynamic equilibrium.
  • Diffusion– After the concentrations at both the ends are equal, the rates at which the particle transfer takes place becomes equal.

Examples of static equilibrium

Static equilibrium is very common and we can observe it in our daily lives. The examples of static equilibrium are given below-

  • Ball resting on ground- The ball is in static condition or at rest. None of the contents in the system are moving and are in static equilibrium.
  • Pen kept on table- The pen is at rest, it needs an external force to move. Hence we can say that the pen is in static equilibrium.
  • Car parked on road- Car will move only if a force (can be anything- force from engine or manual push etc) is applied externally.
  • Student standing on podium– Student standing on the podium is at rest and hence it is in static equilibrium with the podium until he decides to move or someone pushes or pulls him.

What is a closed system?

In very simple words, closed system is a system that does not allow mass transfer transfer from the system to surroundings or vice versa.

The term closed refers to a system that has closed boundaries and does not allow any exchange of mass to take place.

Examples of closed system

The closed system does not allow any mass or energy transfer across its boundaries. The examples of closed system are given below-

  • A bottle with its cap closed- When the bottle cap is closed, mass transfer cannot take place hence it is an example of closed system.
  • A pressure cooker with its lid closed tightly– Mass cannot come out or enter the pressure cooker if the lid is tightly sealed.
  • An air tight zip lock packet– Air tight zip packet is designed in such a way that mass cannot transfer from it. Hence it is an example of a closed system.

What is an open system?

From the name itself, we can imply that open system has its boundaries open for its contents to enter and leave.

A system from which the matter can leave or enter and energy can leave or enter is called as open system. Unlike closed system, the matter and energy (or reactants/products) are lost.

Examples of open system

The following are the examples of an open system-

  • A frying pan– As we can put food inside the pan and take food from it, it is a clear example of open system.
  • An open bottle– Water can come out and enter the an open bottle, hence an open system.
  • Tea filled inside a cup– When we drink tea, it is leaving the cup (system). Hence, it is considered as an open system.
  • Spark ignition engines– The exhaust gases leave the engine, fuel enters the engine. A continuous exchange of matter takes place hence it is an example of an open system.
  • Water pipelines- Water flows in and out of pipelines hence it can be termed as open system.
  • Heat exchangers– Hot fluid and cold fluid enter the heat exchanger hence it is an open system.

Can static equilibrium happen in open systems?

Now we are aware of the meaning of open systems, let us see whether static equilibrium can take place in open systems or not. The description give below explains about it.

For equilibrium to take place, the reactants and products should stop their activities. In open system, it gets easy for mass and energy to get lost. Hence, the reaction that would be taking place will be irreversible. When this irreversible reaction comes to completion, it reaches static equilibrium. So we can say that static equilibrium can take place in open systems.


Hi ....I am Abhishek Khambhata, have pursued B. Tech in Mechanical Engineering. Throughout four years of my engineering, I have designed and flown unmanned aerial vehicles. My forte is fluid mechanics and thermal engineering. My fourth-year project was based on the performance enhancement of unmanned aerial vehicles using solar technology. I would like to connect with like-minded people.

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