Static and Dynamic Equilibrium

When the sum of the forces acting on a rigid body equals zero, the body is said to be in equilibrium. The condition for a body to be in translatory or rotational equilibrium is that net forces and torque with proper components at a point must be zero. The second condition is that the rigid body must not rotate at any specific point. Even when there is a concurrent force system, the body should be at rest or in uniform motion. It should be in balance. Generally, there are two types of equilibrium: dynamic and static equilibrium. In physics, analysing the difference between static and dynamic equilibrium gives some insights into the body’s mechanics. So, let’s get into more detail on the topic.

Major difference between static and dynamic equilibrium

Although a body in dynamic equilibrium may seem at rest, it’s actually in motion. In contrast, a body in static equilibrium remains at rest with an applied external force. The major difference between static and dynamic equilibrium is the state of the body when all the forces are acting upon it. There is no restriction on the number of forces or torque applied to an object in static or dynamic equilibrium, and ΣF = 0 and Στ = 0. The static equilibrium indicates the motionless body, while dynamic equilibrium indicates the continuous change in the body’s motion. In dynamic equilibrium, the body has zero acceleration. This can be proved by Newton’s second law of motion. As F = ma and the net force is equal to zero. Therefore, the object cannot have acceleration. In both conditions, the sum of all the forces equals zero. But an object in static equilibrium does not have velocity. At the same time, objects in dynamic equilibrium have a constant velocity relative to the reference plane. Objects in motion will neither accelerate nor decelerate unless an external force is applied.An object in dynamic equilibrium can move in translator, rotatory or curvilinear motion as compared to the object in static equilibrium.

Importance of the difference between static and dynamic equilibrium:

 

1. For both the practical applications in modern physics, we have outlined the importance of the difference between static and dynamic equilibrium. It is also important to understand the difference between static and dynamic equilibrium for the construction of buildings and bridges. Since architectural structures are stationary, designers prefer their buildings to be static rather than moving. For example, a civil engineer needs to have the desired shape of a bridge and building.
2. The concept of the difference between static and dynamic equilibrium is studied to examine the postures and movements in the human body. Additionally, the study of statics and dynamics is done to determine the forces keeping the human body at a stationary position. For example, a woman with greater body weight in a wheelchair has more inertia than a woman with lower body weight in a wheelchair. Therefore, an aide must exert a greater push on a wheelchair seating a heavyweight woman to get the chair in motion than on the wheelchair seating a lightweight woman.
3. In everyday life, we experience various states of equilibrium. Even the sportsperson who plays tug of war should know about the difference between static and dynamic equilibrium. When two or more individuals pull the rope, the net force applied on both ends should be equal and opposite in direction for the rope to remain stationary.

Examples of static and dynamic equilibrium

There are some common examples of static and dynamic equilibrium. Here are some examples of the differences between static and dynamic equilibrium for a detailed understanding:  

1. The first example is two individuals sitting on a board fixed at a particular point. The board may rotate around the axis if there is a difference between the weight of the individuals. The board will start rotating around the fulcrum and achieve dynamic equilibrium. It would be true if the board moved at a constant speed. But if the two individuals have the same weight, the board will attain a state of equilibrium and remain stationary. It is known as static equilibrium.
2. Tug of war can be a second example to understand the difference between static and dynamic equilibrium. In this game, a rope is pulled between two teams applying a force of equal magnitude but opposite in direction. The rope will be said to be in static equilibrium. But if one of the teams exceeds the value of the force applied by the opposite team, the other team releases the rope. Thus, the rope loses equilibrium.

Conclusion

Static and dynamic equilibrium are phenomena that we experience in our day-to-day life. In fact, they are a part of a number of our daily activities. In this article, we have covered the difference between static and dynamic equilibrium as well as the importance of that difference. The concept of the difference between static and dynamic equilibrium is a core concept and is the heart of the discipline of physics. In this article, we have also covered examples of the difference between static and dynamic equilibrium.