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Wheels (37973)
A wheel is a circular device that is capable of rotating on its axis, facilitating movement or transportation or performing labour in machines. A wheel together with an axle overcomes friction by facilitating motion by rolling. more...
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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 application of another external force. Common examples are found in transport applications. More generally the term is also used for other circular objects that rotate or turn, such as a Ship's wheel and flywheel.
History of the wheel and axle
The English word wheel comes from the Proto-Indo-European *kwekwlo-, which was an extended form of the root *kwel- meaning "to revolve, move around". This is also the root of the Greek κυκλος kuklos, the Sanskrit chakra, and Persian charkh, all meaning "circle" or "wheel", and also in Lithuanian, sukti means "to rotate". The Latin word rota is from the Proto-Indo-European *rotā-, the extended o-grade form of the root *ret- meaning "to roll, revolve".
Origin of wheels
The wheel probably originated in ancient Sumer (modern Iraq) in the 5th millennium BC, originally in the function of potter's wheels. The wheel reached ancient India with the Indus Valley Civilization in the 3rd millennium BC. Near the northern side of the Caucasus several graves were found, in which since 3700 BC people had been buried on wagons or carts (both types). The earliest depiction of what may be a wheeled vehicle (here a wagon—four wheels, two axles), is on the Bronocice pot, a ca. 3500 BC clay pot excavated in southern Poland.
The wheel reached Europe and India (the Indus Valley civilization) in the 4th millennium BC. In China, the wheel is certainly present with the adoption of the chariot in ca. 1200 BC, and Barbieri-Low (2000) argues for earlier Chinese wheeled vehicles, circa 2000 BC. It is an open question whether there was an independent "invention of the wheel" in East Asia. Alternatively the concept may have made its way there after jumping the Himalayan barrier. It has even been suggested that the introduction of the wheel into China was through Chariot wielding conquerors, possibly connected to inception of the Shang Dynasty (ca. 1700 BC).
Read more at Wikipedia.org
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