Rotational motion

Rotational motion is the change in orientation of an object about an axis. In rigid-body rotation, points in the body move along circles centered on that axis.

Angular velocity: The rate at which an object’s angular position changes over time. It measures how quickly rotational motion proceeds.
Angular displacement: The change in angular position, commonly measured in radians. It specifies how far an object turns.
Flywheel: A rotating mechanical device that stores energy as rotational kinetic energy. Its large rotational inertia helps smooth changes in a machine’s speed.
Translational motion: Motion in which every point of a body undergoes the same displacement. It is the principal counterpart to rotation in rigid-body mechanics.
Angular acceleration: The rate of change of angular velocity over time. It describes changes in rotational speed or direction.
Radian: The angle subtended at a circle’s center by an arc equal in length to its radius. Radians make the relation between angular displacement and arc length direct.
Gyroscope: A device that uses a spinning rotor to measure or maintain orientation. Its behavior reveals how angular momentum shapes rotating systems.
Rolling motion: Motion combining rotation of a body with translation of its center of mass. It combines rotational motion with translation rather than involving rotation alone.
Torque: A measure of the tendency of a force to produce rotation about an axis. Applied torque changes rotational motion, much as force changes linear motion.
Circular motion: Motion along a circular path around a fixed center or axis. Points in a rotating rigid body trace circular paths around its axis.

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