motions

Motion is the change in an object's position relative to a reference frame over time. It is described using quantities such as displacement, distance, speed, velocity, and acceleration. A motion description requires choosing a frame of reference; the same event can appear different in different frames.

In kinematics, motion is analyzed without regard to causes. Translational motion refers to linear movement through space, while rotational motion involves spin around an axis. Oscillatory motion repeats in time, as in springs or pendulums. Displacement is the straight-line separation between start and end points, whereas distance is the total path length. Equations relate these quantities to time, often using velocity and acceleration as derivatives of position.

Dynamics studies forces that cause motion. Newton's laws connect force to motion: an object at rest or in uniform motion remains so unless acted on by a net external force; force changes velocity. Momentum, the product of mass and velocity, is conserved in closed systems. Work, energy, and power describe how motion changes due to forces. In many systems, complex motion arises from a combination of translational and rotational components.

In addition to physical motion, the term appears in law and governance. A motion is a formal proposal presented for debate and decision in deliberative assemblies. Motions may require a second, amendments, or procedural rules, and are adopted or rejected by vote.

Motion also appears in science and everyday life beyond mechanics. Brownian motion describes random microscopic movement due to molecular impacts. Biological locomotion covers how organisms move, while in chemistry and materials science, thermal motion relates to molecular agitation.