Equilibrium

A force is a vector quantity, which means it has both a magnitude (size) and a direction associated with it. A force is said to be in equilibrium if both the direction and the magnitude of the forces acting on the object are balanced, meaning there is no net force that is acting on it. Per Newton's first law of motion, an object at rest will stay at rest, and an object in motion will stay in motion. Understanding equilibrium means understanding the basic concepts of forces, torque, and vector physics in general. For testing purposes, and for intuitions in real-life scenarios (e.g., during orthopedic surgery), these concepts are useful to internalize.