Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Rotation shopping experience:

1. Compare - without doubt the biggest advantage that the Rotation offers shoppers today is the ability to compare thousands of Rotation at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Rotation? Wrong! If the Rotation is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Rotation then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Rotation? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Rotation and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Rotation wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Rotation then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Rotation site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Rotation, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Rotation, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

A rotation is a movement of an object in a circular motion. 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 about an external point, e.g. the Earth about the Sun, is called an orbit or more properly an orbital revolution.

Mathematics Mathematics, a rotation is, unlike a translation (geometry), a rigid body movement which keeps a point fixed. This definition applies to rotations within both two and three dimensions (in a plane and in space, respectively.) A rotation in three-dimensional space keeps an entire line fixed, i.e. a rotation in three-dimensional space is a rotation around an axis. This follows from Euler's rotation theorem.

All rigid body movements are rotations, translations, or combinations of the two.

If a rotation around a point or axis is followed by a second rotation around the same point/axis, a third rotation results. The reverse (inverse element) of a rotation is also a rotation. Thus, the rotations around a point/axis form a group (mathematics). However, a rotation around a point or axis and a rotation around a different point/axis may result in something other than a rotation, e.g. a translation.

Rotations around the x, y and z axes are called principal rotations. Rotation around any axis can be performed by taking a rotation around the x axis, followed by a rotation around the y axis, and followed by a rotation around the z axis. That is to say, any spatial rotation can be decomposed into a combination of principal rotations.

In flight dynamics, the principal rotations are known as pitch, roll and yaw (known as Tait-Bryan angles). This terminology is also used in computer graphics.

==Astronomy==

In astronomy, rotation is a commonly observed phenomenon. Stars, planets and similar bodies all spin around on their Axis (the plural of axis). The rotation rate of planets in the solar system was first measured by tracking visual features. Stellar rotation is measured through Doppler shift or by tracking active surface features.

This rotation induces a centrifugal acceleration which slightly counteracts the effect of gravity the closer one is to the equator. One effect is that an object weighs slightly less at the equator. Another is that the Earth is slightly deformed into an oblate spheroid.

Another consequence of the rotation of a planet is the phenomenon of precession. Like a gyroscope, the overall effect is a slight "wobble" in the movement of the axis of a planet. Currently the tilt of the Earth's axis to its orbital plane (obliquity of the ecliptic) is 23.45 degrees, but this angle changes slowly (over thousands of years). (See also Precession of the equinoxes and Pole star.)

Rotation and revolution While revolution is often used as a synonym for rotation, in many fields, particularly astronomy and related fields, revolution, often referred to as orbital revolution for clarity, is used when one body moves around another while rotation is used to mean the movement around an axis. Moons revolve about their planet, planets revolve about their star (such as the Earth around the Sun); and stars slowly revolve about their galaxial center. The motion of the components of galaxy is complex, but it usually includes a rotation component.

The Moon makes one complete rotation during one complete orbital revolution around the Earth (an effect called tidal locking) so that the same side of the Moon always faces the Earth (the other side is called the far side of the Moon).

Retrograde rotation Most planets in our solar system, including Earth, spin in the same direction as they orbit the Sun. The exceptions are Venus and Uranus. Uranus rotates nearly on its side relative to its orbit. Current speculation is that Uranus started off with a typical prograde orientation and was knocked on its side by a large impact early in its history. Venus may be thought of as rotating slowly backwards (or being "upside down"). The dwarf planet Pluto (formerly considered a planet) is anomalous in this and other ways.

Physics The speed of rotation is given by the angular frequency (rad/s) or frequency (turn (geometry)/s, turns/min), or periodicity (seconds, days, etc.). The time-rate of change of angular frequency is angular acceleration (rad/s²), This change is caused by torque. The ratio of the two (how heavy is it to start, stop, or otherwise change rotation) is given by the moment of inertia.

The angular velocity vector also describes the direction of the axis of rotation. Similarly the torque is a vector.

According to the right-hand rule, the direction away from the observer is associated with clockwise rotation and the direction towards the observer with counterclockwise rotation, like a screw.

Aviation In flight dynamics, the principal rotations are known as pitch, roll and yaw. The term rotation is also used in aviation to refer to the upward pitch (nose moves up) of an aircraft, particularly when starting the climb after takeoff.

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. As a result at any time the orientation of the gondola is upright (not rotated), just translated. The tip of the translation vector describes a circle. A carousel provides rotation about a vertical axis. Many rides provide a combination of rotations about several axes. In Chair-O-Planes the rotation about the vertical axis is provided mechanically, while the rotation about the horizontal axis is due to the centrifugal force. In Roller coaster inversion the rotation about the horizontal axis is one or more full cycles, where the centrifugal force keeps people in their seats.

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. 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.

External links

• Product of Rotations at cut-the-knot
• When a Triangle is Equilateral at cut-the-knot

• Rotate Points Using Polar Coordinates

A rotation is a movement of an object in a circular motion. 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 about an external point, e.g. the Earth about the Sun, is called an orbit or more properly an orbital revolution.

Mathematics Mathematics, a rotation is, unlike a translation (geometry), a rigid body movement which keeps a point fixed. This definition applies to rotations within both two and three dimensions (in a plane and in space, respectively.) A rotation in three-dimensional space keeps an entire line fixed, i.e. a rotation in three-dimensional space is a rotation around an axis. This follows from Euler's rotation theorem.

All rigid body movements are rotations, translations, or combinations of the two.

If a rotation around a point or axis is followed by a second rotation around the same point/axis, a third rotation results. The reverse (inverse element) of a rotation is also a rotation. Thus, the rotations around a point/axis form a group (mathematics). However, a rotation around a point or axis and a rotation around a different point/axis may result in something other than a rotation, e.g. a translation.

Rotations around the x, y and z axes are called principal rotations. Rotation around any axis can be performed by taking a rotation around the x axis, followed by a rotation around the y axis, and followed by a rotation around the z axis. That is to say, any spatial rotation can be decomposed into a combination of principal rotations.

In flight dynamics, the principal rotations are known as pitch, roll and yaw (known as Tait-Bryan angles). This terminology is also used in computer graphics.

==Astronomy==

In astronomy, rotation is a commonly observed phenomenon. Stars, planets and similar bodies all spin around on their Axis (the plural of axis). The rotation rate of planets in the solar system was first measured by tracking visual features. Stellar rotation is measured through Doppler shift or by tracking active surface features.

This rotation induces a centrifugal acceleration which slightly counteracts the effect of gravity the closer one is to the equator. One effect is that an object weighs slightly less at the equator. Another is that the Earth is slightly deformed into an oblate spheroid.

Another consequence of the rotation of a planet is the phenomenon of precession. Like a gyroscope, the overall effect is a slight "wobble" in the movement of the axis of a planet. Currently the tilt of the Earth's axis to its orbital plane (obliquity of the ecliptic) is 23.45 degrees, but this angle changes slowly (over thousands of years). (See also Precession of the equinoxes and Pole star.)

Rotation and revolution While revolution is often used as a synonym for rotation, in many fields, particularly astronomy and related fields, revolution, often referred to as orbital revolution for clarity, is used when one body moves around another while rotation is used to mean the movement around an axis. Moons revolve about their planet, planets revolve about their star (such as the Earth around the Sun); and stars slowly revolve about their galaxial center. The motion of the components of galaxy is complex, but it usually includes a rotation component.

The Moon makes one complete rotation during one complete orbital revolution around the Earth (an effect called tidal locking) so that the same side of the Moon always faces the Earth (the other side is called the far side of the Moon).

Retrograde rotation Most planets in our solar system, including Earth, spin in the same direction as they orbit the Sun. The exceptions are Venus and Uranus. Uranus rotates nearly on its side relative to its orbit. Current speculation is that Uranus started off with a typical prograde orientation and was knocked on its side by a large impact early in its history. Venus may be thought of as rotating slowly backwards (or being "upside down"). The dwarf planet Pluto (formerly considered a planet) is anomalous in this and other ways.

Physics The speed of rotation is given by the angular frequency (rad/s) or frequency (turn (geometry)/s, turns/min), or periodicity (seconds, days, etc.). The time-rate of change of angular frequency is angular acceleration (rad/s²), This change is caused by torque. The ratio of the two (how heavy is it to start, stop, or otherwise change rotation) is given by the moment of inertia.

The angular velocity vector also describes the direction of the axis of rotation. Similarly the torque is a vector.

According to the right-hand rule, the direction away from the observer is associated with clockwise rotation and the direction towards the observer with counterclockwise rotation, like a screw.

Aviation In flight dynamics, the principal rotations are known as pitch, roll and yaw. The term rotation is also used in aviation to refer to the upward pitch (nose moves up) of an aircraft, particularly when starting the climb after takeoff.

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. As a result at any time the orientation of the gondola is upright (not rotated), just translated. The tip of the translation vector describes a circle. A carousel provides rotation about a vertical axis. Many rides provide a combination of rotations about several axes. In Chair-O-Planes the rotation about the vertical axis is provided mechanically, while the rotation about the horizontal axis is due to the centrifugal force. In Roller coaster inversion the rotation about the horizontal axis is one or more full cycles, where the centrifugal force keeps people in their seats.

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. 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.

External links

• Product of Rotations at cut-the-knot
• When a Triangle is Equilateral at cut-the-knot

• Rotate Points Using Polar Coordinates

Rotation - Wikipedia, the free encyclopedia
A rotation is a movement of an object in a circular motion. A two-dimensional object rotates around a center (or point) of rotation. A three-dimensional object rotates around a ...

Earth's rotation - Wikipedia, the free encyclopedia
Earth's rotation is the rotation of the solid Earth around its own axis. The Earth rotates towards the east, which can be observed by orientation with a magnetic compass at sunrise ...

rotation

Tyres :: Tyre rotation
Tyre balancing and rotation, how wear effects your tyres.. ... Tyre rotation. Many tyre manufacturers agree that it is no longer good practice to rotate your tyres in order to ...

MathsNet Rotation
Note: if this message appears, please enable Java before you continue.

Definition: rotation from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.

backup rotation from FOLDOC
backup rotation < operating system > Any system for re-using backup media, e.g. magnetic tape. One extreme would be to use the same media for every backup (e.g. copy disk A to disk ...

Rotation Illusions
Demonstration of Peter Thompson's Thatcher illusion ... Some things change completely when turned upside down. Start the QuickTime when it has finished loading and observe: the ...

Royal Horticultural Society - Gardening Advice: Crop Rotation
The principle of crop rotation is to grow specific groups of vegetables on a different piece of land each year. Groups are moved around in sequence so they don't return to the same ...

BBC - Gardening - Grow your own - Plot rotation
Plot rotation in vegetable growing ... Plot rotation. A good, healthy vegetable plot is essential if you're planning to grow your own.