9 Dynamic Equilibrium Example: Detailed Explanations

This article focuses on dynamic equilibrium example. We have an idea of what equilibrium is, we will read in detail about its type- Dynamic equilibrium in this article.

The word dynamic refers to something which is having mobility. And equilibrium is related to stability and balance. We can say that dynamic equilibrium refers to something which is mobile and stable. We will study further about dynamic equilibrium in this article.

What is dynamic equilibrium?

In Physics/Chemistry, dynamic equilibrium occurs in a reversible chemical reaction. In this type of reaction, the formation of both reactants and products occurs at same rate. In a nutshell, backward and forward reaction occur at same rates.

Hence, the net content of both reactants and products remain same. This is also called as steady state sometimes. Thus we can say that things are dynamic in nature but has a balance too. In thermodynamics, this is called as thermodynamic equilibrium where reactions occur at such a rate that composition of mixture does not change significantly.

Dynamic equilibrium example

We know the meaning of dynamic equilibrium. There are various places where we can see dynamic equilibrium taking place in our every day lives. Lets get a clearer idea of what exactly dynamic equilibrium is by looking at its examples.

Dissociation of acetic acid in an aqueous solution

Rate of formation of reactants is equal to  rate of formation of products hence the net content of the system is same. This is why it is said to be in neutral equilibrium.

dynamic equilibrium example
Image: % concentrations of species in isomerization reaction

Image credits: Wikipedia

Train running with constant speed

When the train running with constant speed, the friction is balanced with the forward force applied by the train. At constant velocity, the magnitude of forces are not changed.

Aeroplane flying at constant speed

The upthrust is equal to the force due to gravity. No other change is observed hence it is dynamic equilibrium.

Car moving at constant velocity

The weight is balanced by reaction force and forward force is balanced by friction. Also the forward force is opposed by friction with equal rate. No other change in force is observed. The net force remains the same hence it is said to be in dynamic equilibrium.

Running on a treadmill at constant speed

The forward movement of legs is equal to the backward movement of treadmill floor leaving the human running at the same place hence these forces balance each other and makes the person running on the treadmill and the treadmill itself are in dynamic equilibrium. (Considering both as one system).

Free falling body after it has achieved terminal velocity

After achieving terminal velocity, all the forces are balanced and do not change even with downward movement of the free falling object.

Number of cars entering and leaving the city at the same rate

Particles entering and leaving the system at the same rate is an example of dynamic equilibrium. Here the number of cars entering and leaving the city are same. Considering city as a system, the city is in dynamic equilibrium.

A steady flow of water in pipe

The rate at which water is entering the pipe is equal to the rate at which water is leaving the pipe. Hence the pipe as a system is in dynamic equilibrium.

Heat transfer in heat exchanger

The heat absorbed by the cold fluid is equal to the heat left by the hotter fluid. Hence the pipes of heat exchanger in terms of heat transfer is in dynamic equilibrium. If we look at the mass flow rates at inlet and outlet and they both are same, we can say that entire heat exchanger is in dynamic equilibrium.

Rectilinear motion of bodies

Like trains and cars, their rectilinear motion makes them in dynamic equilibrium. In rectilinear motion having constant velocity, the net forces acting in the system remain same so the system is in dynamic equilibrium.

Difference between static equilibrium and dynamic equilibrium

The major difference between both these equilibriums is the mobility of particles/objects in the system.

In dynamic equilibrium, the rate of particles/objects entering the system is equal to the rate of particles/objects leaving the system. Here we can say the contents of this system are in continuous state of motion. In static equilibrium, the object is at rest and in equilibrium. This means there is no mobility of the contents in the system.

What is static equilibrium?

Static equilibrium is a state of equilibrium attained by bodies when they are at rest. In this case also, the sum of all forces acting on the body is zero.

If for example, an elephant is pulling one end of an inelastic rope in x direction and a truck is pulling other end in -x direction with the same magnitude of force, then the rope does not displace from its original position. This is the best example of static equilibrium.


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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