Wheel
A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle bearing.
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.
Cognates within Indo-European include Icelandic hjól 'wheel, tyre', Greek κύκλος kúklos, and Sanskrit chakra, the last two both meaning 'circle' or 'wheel'.
[11][12] The invention of the solid wooden disk wheel falls into the late Neolithic, and may be seen in conjunction with other technological advances that gave rise to the early Bronze Age.
[14] The oldest surviving example of a potter's wheel was thought to be one found in Ur (modern day Iraq) dating to approximately 3100 BCE.
[10][16][8][17][7][18] Wheels of uncertain dates have been found in the Indus Valley civilization of the late 4th millennium BCE covering areas of present-day India and Pakistan.
[20][21][22] In Mesopotamia, depictions of wheeled wagons found on clay tablet pictographs at the Eanna district of Uruk, in the Sumerian civilization are dated to c. 3500–3350 BCE.
Depictions of a wheeled vehicle appeared between 3631 and 3380 BCE in the Bronocice clay pot excavated in a Funnelbeaker culture settlement in southern Poland.
The earliest known examples of wooden spoked wheels are in the context of the Sintashta culture, dating to c. 2000 BCE (Krivoye Lake).
Soon after this, horse cultures of the Caucasus region used horse-drawn spoked-wheel war chariots for the greater part of three centuries.
They moved deep into the Greek peninsula where they joined with the existing Mediterranean peoples to give rise, eventually, to classical Greece after the breaking of Minoan dominance and consolidations led by pre-classical Sparta and Athens.
[30][31][32] In Britain, a large wooden wheel, measuring about 1 m (3.3 ft) in diameter, was uncovered at the Must Farm site in East Anglia in 2016.
[43] Starting from the 18th century in West Africa, wheeled vehicles were mostly used for ceremonial purposes in places like Dahomey.
More modern descendants of the wheel include the propeller, the jet engine, the flywheel (gyroscope) and the turbine.
The low resistance to motion is explained by the fact that the frictional work done is no longer at the surface that the vehicle is traversing, but in the bearings.
Even with a plain bearing, the frictional work is greatly reduced because: Example: Additional energy is lost from the wheel-to-road interface.
It depends on the nature of the ground, of the material of the wheel, its inflation in the case of a tire, the net torque exerted by the eventual engine, and many other factors.
[47] It makes up the outer circular design of the wheel on which the inside edge of the tire is mounted on vehicles such as automobiles.
The radial members of a wagon wheel were made by carving a spoke (from a log) into their finished shape.
Before rubber was invented, the first versions of tires were simply bands of metal that fitted around wooden wheels to prevent wear and tear.
Examples include: Truck and bus wheels may block (stop rotating) under certain circumstances, such as brake system failure.
To help detect this, they sometimes feature "wheel rotation indicators": colored strips of plastic attached to the rim and protruding out from it, such that they can be seen by the driver in the side-view mirrors.
The introduction of spoked (chariot) wheels in the Middle Bronze Age appears to have carried somewhat of a prestige.
[54]In modern usage, the 'invention of the wheel' can be considered as a symbol of one of the first technologies of early civilization, alongside farming and metalwork, and thus be used as a benchmark to grade the level of societal progress.
