角度量と線形量の関係 - II

Centripetal acceleration is the radial component associated with changes in velocity direction, pointing inward toward the axis of rotation. Tangential acceleration is parallel to instantaneous velocity and relates to changes in speed magnitude. These two components are always perpendicular to each other and together form the total linear acceleration in nonuniform circular motion.

Centripetal acceleration can be expressed in terms of angular velocity by replacing linear velocity with omega times radius. This relationship shows that centripetal acceleration depends on both the angular velocity and the distance from the axis of rotation. The resulting formula connects the radial acceleration component directly to rotational motion parameters.

Tangential acceleration is associated only with changes in speed, not direction, making it directly related to angular acceleration. Angular acceleration is positive when angular velocity increases, causing positive tangential acceleration, and negative when angular velocity decreases. This relationship shows how rotational acceleration manifests as linear acceleration along the circular path.

In uniform circular motion, angular velocity is constant and angular acceleration is zero, so tangential acceleration is absent. The only linear acceleration present is centripetal acceleration, which continuously changes the velocity direction while maintaining constant speed. This occurs because there is no change in the magnitude of tangential velocity, only its direction.

Total linear acceleration is the vector sum of centripetal and tangential acceleration components. Since these components are perpendicular, the resultant vector points at an angle between them. This combined acceleration vector describes the complete change in velocity for a point on a rotating rigid body or particle executing nonuniform circular motion.

The linear tangential speed of a particle at a radius from the axis of rotation is related to angular velocity by the relation v equals omega times r. This relationship applies to both individual particles and points on rigid bodies rotating about a fixed axis. Replacing velocity with this expression allows conversion between linear and angular motion quantities.

Uniform circular motion exhibits only centripetal acceleration because angular velocity remains constant. Nonuniform circular motion has both centripetal and tangential acceleration components due to angular acceleration. The presence of tangential acceleration in nonuniform motion indicates that the rotating system is speeding up or slowing down while changing direction.