Wheel

A wheel is a circular component that is intended to rotate on an axle bearing. The wheel is one of the main components of the wheel and axle which is one of the six simple machines. Wheels, in conjunction with axles, allow heavy objects to be moved easily facilitating movement or transportation while supporting a load, or performing labor in machines. Wheels are also used for other purposes, such as a ship's wheel, steering wheel, potter's wheel and flywheel.

Common examples are found in transport applications. A wheel greatly reduces friction by facilitating motion by rolling together with the use of axles. In order for wheels to rotate, a moment needs to be applied to the wheel about its axis, either by way of gravity, or by the application of another external force or torque.

Etymology

The English word wheel comes from the Old English word hweol, hweogol, from Proto-Germanic *hwehwlan, *hwegwlan, from Proto-Indo-European *k^wek^wlo-, an extended form of the root *k^wel- "to revolve, move around". Cognates within Indo-European include Icelandic hjól "wheel, tyre", Greek κύκλος kúklos, and Sanskrit chakra, the latter both meaning "circle" or "wheel".

Wheel calculator

A wheel calculator is made of concentric paper or plastic discs, used to make calculations involving time periods. They have applications in pregnancy (to calculate the due date) and insurance.

Online wheel calculator

An Internet web site that may be used for insurance cancellation calculations providing an alternative to the manual paper wheel calculators. The online wheel calculator can be used to calculate all three cancellation methods including pro rata, short rate and short rate (90% pro rata). Also provided is the earned and unearned premium.

Paper wheel calculator

A circular calculator made out of paper and plastic disks that works similar to a circular slide rule. It has a base line that is aligned with the inception date of the insurance policy. An arm on the wheel is then aligned with the cancellation date of the policy. The number of elapsed days, pro rata and short rate factors, both earned and unearned, are indicated by the arm in proper column. The policy premium is multiplied by the factor to calculate either the earned or unearned premium.

Wheel (Unix term)

In computing, the term wheel refers to a user account with a wheel bit, a system setting that provides additional special system privileges that empower a user to execute restricted commands that ordinary user accounts cannot access. The term is derived from the slang phrase big wheel, referring to a person with great power or influence. It was first used in this context with regard to the TENEX operating system, later distributed under the name TOPS-20 in the 1960s and early 1970s.

The term was adopted by Unix users in the 1980s, due to the movement of operating system developers and users from TENEX/TOPS-20 to Unix. Modern Unix implementations generally include a security protocol that requires a user to be a member of the wheel user privileges group in order to gain superuser access to a machine by using the su command.

Wheel group

Modern Unix systems use user groups to control access privileges. The wheel group is a special user group used on some Unix systems to control access to the su command, which allows a user to masquerade as another user (usually the super user).