What is Dynamic Equilibrium

Equilibrium of a particle in physics is defined as a state in which the opposing forces on a system are balanced. It can also be defined as a situation in which the internal energy and body’s motion do not change. Therefore, the changes in the motion must be produced by external forces. The net force on the system equals zero; as we know by Newton’s first law of motion, a body can either be at rest or in motion. The acceleration and sum of all the external forces on the body are zero. 

For example, when you observe a car in motion, you will notice that it moves with a constant velocity on a straight road. This means that the car has no net external force acting on it. In other words, this equilibrium is classified as dynamic equilibrium. Let’s take a look at the introduction to dynamic equilibrium.

Introduction to Dynamic Equilibrium

To start with, let’s first understand the different types of equilibrium. Equilibrium is a uniform phenomenon classified into two different types, including static and dynamic equilibrium. But what is the difference between the two? This can be best understood with an example.

Suppose an object A moves at a constant speed with all the forces in balance. Object A continues to move at a constant speed until the horizontal force balances the frictional force. Horizontal force should be in the direction of motion, while frictional force is in the opposite direction. So object A is in dynamic equilibrium.

On the other hand, there is another object B on which two forces are acting from the right and left. The magnitude of both the forces should be equal but opposite in direction. Thus, object B will be in a stationary state or at rest. It does not move due to the balanced forces. In this case, the object is in static equilibrium. 

Let’s understand the meaning of dynamic equilibrium in detail. 

What is Dynamic Equilibrium?

So if we analyse an object in translational or rotational motion, it can attain dynamic equilibrium. In translatory motion, the vector sum of all the forces must be zero. Therefore, the acceleration will also be equal to zero as F = ma.

∑ Fx = 0 ∑ Fy = 0

The net external torque applied to the body must be zero in the rotatory motion. Thus, it can be written as: 

∑τ = 0

 Let us now try to understand the meaning of dynamic equilibrium. In both translational and rotational motion, the body is in equilibrium as it continues to move with a uniform velocity. So, in dynamic equilibrium, the net external force and torque are zero.

The next question that will come to your mind is determining whether the forces are balanced or not. The forces acting on a body can be in any direction. Remember that one force has two components, usually at right angles i.e. in the x and y direction. This is because force is a vector quantity with both magnitude and direction. Also, this type of force system is known as a concurrent force system. 

Consider the following situation:

A person pulls a car at some angle. It is moving at a constant speed on a straight road, so there is some frictional force F1 resisting the car’s motion. Also, there will be tension F2 produced in the rope due to the pull and friction as an opposing force. In this situation, you need to make two components in the F2x and F2y direction of the tension in the rope as it has some angle with the ground. There will also be a force F3, considered as the gravitational force acting downwards. F2y is the normal force from the ground acting on the car in reaction to F3. 

So, the vector sum of all the four forces must be zero.

F1 + F2x + F2y + F3 = 0

Dynamic Equilibrium Applications

Civil engineers usually use dynamic equilibrium to build structures. It is important to consider this type of equilibrium for a body’s balance when it is in motion. Additionally, dynamic equilibrium plays an important role in lifting the materials with the help of straps. The tension in the rope used to lift heavy objects should exert a huge amount of force to prevent the falling of the objects. Therefore, it is important to manufacture the ropes and consider the weight they can lift against gravity. This makes sure that the rigging doesn’t fail. 

Conclusion

Dynamic equilibrium is an important phenomenon in our everyday life. Now engineers can solve the problems of mechanics with its help. Here, we covered a detailed introduction to dynamic equilibrium. We have also explored the meaning of dynamic equilibrium and its applications. Further, there are a few situations of evidence that prove its credibility. You will also know where dynamic equilibrium is taken into use. Finally, you can get more information through the notes we have prepared for all the students.