What is meant by equilibrium in physics?

Equilibrium in physics means a state where all forces and moments acting on a system are balanced.

In more detail, equilibrium can be divided into two main types: static and dynamic. Static equilibrium occurs when an object is at rest, and all the forces acting on it are balanced. For example, a book lying on a table is in static equilibrium because the gravitational force pulling it down is balanced by the normal force from the table pushing it up.

Dynamic equilibrium, on the other hand, happens when an object is moving at a constant velocity. In this case, the forces acting on the object are still balanced, but the object is not at rest. For instance, a car cruising at a constant speed on a straight road is in dynamic equilibrium because the forward force from the engine is balanced by the resistive forces like air resistance and friction.

To determine if an object is in equilibrium, we use two main conditions. The first condition is that the sum of all the forces acting on the object must be zero. This is known as the translational equilibrium condition. Mathematically, it can be written as ΣF = 0, where ΣF represents the sum of all forces.

The second condition is that the sum of all the moments (or torques) acting on the object must also be zero. This is known as the rotational equilibrium condition. Mathematically, it can be expressed as Στ = 0, where Στ represents the sum of all moments.

Understanding equilibrium is crucial in physics because it helps us analyse and predict the behaviour of objects in various situations. Whether designing a stable bridge or ensuring a satellite remains in a stable orbit, the principles of equilibrium are fundamental to solving real-world problems.