Equilibrium is a state where a system is balanced and experiences no net force.

Equilibrium refers to a condition in which all forces acting on an object are balanced, resulting in no net force and, consequently, no acceleration. This concept can apply to various contexts, such as physics, chemistry, and economics.

1. Mechanical Equilibrium: In physics, an object is said to be in mechanical equilibrium if the sum of all forces and the sum of all torques acting on it are zero. This can be expressed mathematically as: $\sum \vec{F} = 0 \quad \text{and} \quad \sum \vec{\tau} = 0$ This implies that the object will either remain at rest or continue to move with a constant velocity if it was in motion.

2. Chemical Equilibrium: In chemistry, equilibrium can refer to a state in a reversible reaction where the rate of the forward reaction equals the rate of the backward reaction, resulting in constant concentrations of reactants and products. For a reaction $aA + bB \leftrightarrow cC + dD$, the equilibrium constant $K$ can be defined as: $K = \frac{[C]^c [D]^d}{[A]^a [B]^b}$

3. Economic Equilibrium: In economics, equilibrium refers to a state where supply equals demand, meaning there is no tendency for change in price. This can be analyzed using supply and demand curves, where the intersection point indicates the equilibrium price and quantity.

Understanding equilibrium in these contexts helps analyze the stability of systems, predict behaviors, and design interventions when necessary. It is a fundamental concept that underlies many physical laws and theories, contributing to a deeper comprehension of both natural and man-made systems.