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How does equilibrium occur when all forces acting on an object are balanced?

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Title page of Isaac Newton's Philosophiae Naturalis Principia Mathematica, 1687, featuring large Latin text and publication details in a bordered layout. — Newton’s laws of motion The title page of Isaac Newton's *Philosophiae Naturalis Principia Mathematica* (1687; *Mathematical Principles of Natural Philosophy*), the work in which the physicist introduced his three laws of motion.

In the context of Newton’s laws of motion, an object is in equilibrium when it experiences no net force, meaning all forces acting upon it are precisely balanced. According to Newton’s second law, an object with a net force undergoes acceleration; conversely, if the vector sum of all forces is zero, the object does not accelerate and maintains a constant state of motion or rest.12

For a single particle, equilibrium occurs simply when the vector sum of all forces is zero. For a rigid body, equilibrium requires two conditions:2
* The vector sum of all forces acting on the body must be zero.23
* The vector sum of all torques acting on the body with respect to any point must be zero, ensuring the object's rotational motion remains constant.23

When these conditions are met, the object is in an immobile or steady state, as seen when a stationary object rests on a surface, where the downward force of gravity is balanced by an equal and opposite upward force exerted by the surface.1