What branch of physics treats Newton's laws as basic laws of motion?

The branch of physics that treats Newton’s laws as basic laws of motion is classical mechanics. It describes the movement of ordinary, macroscopic objects using concepts such as force, mass, acceleration, momentum and energy.

Newton presented his three laws in the Principia Mathematica, first published in 1687. Together with his law of universal gravitation, they supplied a mathematical framework for explaining both everyday motion and celestial events, including planetary orbits and falling bodies.

Classical mechanics later developed beyond Newton’s original formulation. Lagrangian and Hamiltonian mechanics recast the same physical ideas using energy, action and generalized coordinates, making difficult problems easier to analyze. These approaches remain central in physics and engineering.

Classical mechanics has limits. Relativity is needed for objects moving near light speed or in strong gravitational fields, while quantum mechanics governs atomic and subatomic behavior. Those theories do not erase Newton’s laws; they show when the classical approximation works and when a deeper description is required.