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The wheel and axle is one of six simple machines identified by Renaissance scientists drawing from Greek texts on technology.〔Wheel and Axle, The World Book Encyclopedia, World Book Inc., 1998, pp. 280-281〕 The wheel and axle is generally considered to be a wheel attached to an axle so that these two parts rotate together in which a force is transferred from one to the other. In this configuration a hinge, or bearing, supports the rotation of the axle. Hero of Alexandria identified the wheel and axle as one of the six simple machines used to lift weights. This is thought to have been in the form of windlass which consists of a crank or pulley connected to a cylindrical barrel that provides mechanical advantage to wind up a rope and lift a load such as a bucket from of well.〔Elroy McKendree Avery, (Elementary Physics ), New York : Sheldon & Company, 1878.〕 This system is a version of the lever with loads applied tangentially to the perimiter of the wheel and axle, respectively, that are balanced around the hinge, which is the fulcrum. The mechanical advantage of the wheel and axle is the ratio of the distances from the fulcrum to the applied loads, or what is the same thing the ratio of the radial dimensions of the wheel and axle.〔Bowser, Edward Albert, 1890, ( An elementary treatise on analytic mechanics: with numerous examples. ) (Originally from the University of Michigan) D. Van Nostrand Company, pp. 190〕 ==History== The earliest well-dated depiction of a wheeled vehicle (a wagon—four wheels, two axles) is on the Bronocice pot, a ca. 3635–3370 BC ceramic vase, excavated in a Funnelbeaker culture settlement in southern Poland. The oldest known example of a wooden wheel and its axle was found in 2002 at the Ljubljana Marshes some 20 km south of Ljubljana, the capital of Slovenia. According to radiocarbon dating, it is between 5,100 and 5,350 years old. The wheel was made of ash and oak and had a radius of 70 cm and the axle is 120 cm long and made of oak. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「wheel and axle」の詳細全文を読む スポンサード リンク
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