# Dynamic Balance

The word dynamic refers to something that has mobility. And balance is related to stability and balance. We can say that dynamic equilibrium refers to something that is moving and stationary. We will study more 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, both the reactant and the product are produced at the same rate. In short, back and forth reactions occur at similar rates.

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

## dynamic balance example

We know the meaning of dynamic equilibrium. There are many places where we can see dynamic equilibrium happening in our daily life. Let’s look at examples of this to get a clear idea of ​​what dynamic equilibrium actually is.

## dissociation of acetic acid in aqueous solution

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

## train running at constant speed

When the train moves at a constant speed, the friction is balanced with the forward force exerted by the train. With a constant velocity, there is no change in the magnitude of the forces.

## airplane flying at constant speed

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

## car moving at constant speed

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

## running on a treadmill at a constant speed

The forward movement of the legs is equal to the backward movement of the treadmill floor, so that the human running in the same position, these forces balance each other and keep the person running on the treadmill in dynamic equilibrium. (Assuming both as one system).

## Free falling body after attaining terminal velocity

After attaining the final velocity, all the forces become balanced and do not change even when the freely falling object moves downwards.

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

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

## a steady flow of water in a pipe

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

## heat transfer in heat exchanger

RSI The heat absorbed by the cold liquid is equal to the heat dissipated by the hot liquid. Therefore, the heat exchanger pipes are in dynamic equilibrium with respect to heat transfer. If we look at the mass flow rates at the inlet and outlet and they are both the same, we can say that the entire heat exchanger is in dynamic equilibrium.

## straight line motion of bodies

Like trains and cars, their straight motion makes them in dynamic equilibrium. In straight line motion with uniform velocity, the net force acting in the system remains the same, so the system is in dynamic equilibrium.

## difference between static equilibrium and dynamic equilibrium

The main difference between these two equilibria is the mobility of the 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 that the material of this system is in a state of constant motion. In stationary equilibrium, the object is at rest and in equilibrium. This means that there is no mobility of the material in the system.

## What is stable equilibrium?

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

For example, if an elephant is pulling one end of an elastic rope in the x direction and a truck is pulling the other end in the -x direction with equal force, the rope is not displaced from its original position. This is the best example of static equilibrium.