Rotation

Rotation is the movement of an object in a circular motion.

A sphere rotating around its axis

A two-dimensional object rotates around a center (or point) of rotation. A three-dimensional object rotates around a line called an 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

The Clockwise direction

Rotation around a point in one plane can be in a clockwise direction or an 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 rides 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 and pool. Curve balls 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

• Earth's spin
• Precession
• Torque

Other websites

• Product of Rotations at cut-the-knot
• When a Triangle is Equilateral at cut-the-knot
• Rotation (Interactive Animation) at Math is Fun
• Rotate Points Using Polar Coordinates Archived 2007-02-20 at the Wayback Machine