What is Rotation?
[[Image:Rotating Sphere.gif|right|thumb|A sphere rotating around its axis]] '''Rotation''' is the movement of an object in a circular [[Movement|motion]]. A two-[[dimension]]al object rotates around a ''center'' (or ''[[point (geometry)|point]]'') ''of rotation''. A three-dimensional object rotates around a line called an ''[[Axis (mathematics)|axis]]''. If the [[axis of rotation]] is within the body, the body is said to rotate upon itself, or ''spin''– which implies relative [[speed]] and perhaps free-movement with [[angular momentum]]. A circular motion around an external point (for example the [[Earth]] around the [[Sun]]) is called an ''[[orbit]]'' or more properly ''[[orbital revolution]].'' As an extension, 4d rotations are around planes. Every rotation can also be described as in a plane and around a point. ==Types of rotation== [[Image:Uhrzeigersinn.png|thumb|right|100px|The Clockwise direction]] Rotation around a point in one plane can be in a [[clockwise]] direction or an [[clockwise|anticlockwise]] direction. ===Aviation=== In [[flight dynamics]], the principal rotations are known as ''yaw'' (left/right), ''pitch'' (up/down), and ''roll'' (rolling). The term rotation is also used in aviation to refer to the upward pitch of an aircraft, particularly when starting the major climb for takeoff. The same terms are used for fish moving through water. ===Amusement rides=== Many [[amusement ride]]s provide rotation. A [[Ferris wheel]] and [[observation wheel]] have a horizontal central axis, and parallel axes for each gondola, where the rotation is opposite, by gravity or mechanically. ===Sports=== Rotation, usually called ''spin'', plays a role in many sports. ''Topspin'' and ''backspin'' in [[tennis]]. ''English'', ''follow'' and ''draw'' in [[Billiards#Shooting techniques/mechanics|billiards and pool]]. [[Curve ball]]s in baseball and [[spin bowling]] in cricket. [[Table tennis]] paddles are specialized to allow players to spin the ball as they hit it. == Related pages == *[[Precession]] *[[Torque