A wheel is a rotating component (typically circular in shape) that is intended to turn on an axlebearing. The wheel is one of the key 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 can be found in transport applications. A wheel 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. Using the wheel, Sumerians invented a device that spins clay as a potter shapes it into the desired object. (Full article...)
Image 9Interior view of a high-speed bullet train, manufactured in China (from Rail transport)
Image 10Arizona - North America - Southwest - Interstate Highway System (4893585908) (from Road transport)
Image 11San Diego Trolley over Interstate 8 (from Road transport)
Image 12German soldiers in a railway car on the way to the front in August 1914. The message on the car reads Von München über Metz nach Paris ("From Munich via Metz to Paris"). (from Rail transport)
Image 18Lilienthal in mid-flight, Berlin c. 1895 (from Aviation)
Image 19The Cessna 172 is the most produced aircraft in history (from Aviation)
Image 20The Polish transport company Bedmet uses a special vehicle to transport two large silos. (from Road transport)
Image 21A 16th-century minecart, an early example of unpowered rail transport (from Rail transport)
Image 22The Lockheed SR-71 remains unsurpassed in many areas of performance. (from Aviation)
Image 23Map of world railway network as of 2022 (from Rail transport)
Image 24Bridges, such as Golden Gate Bridge, allow roads and railways to cross bodies of water. (from Transport)
Image 25Tunnels, such as the Tampere Tunnel, allow traffic to pass underground or through rock formations. (from Transport)
Image 26Bulk cargo of minerals on a train (from Rail transport)
Image 27According to Eurostat and the European Railway Agency, the fatality risk for passengers and occupants on European railways is 28 times lower when compared with car usage (based on data by EU-27 member nations, 2008–2010). (from Rail transport)
Image 31Bardon Hill box in England (seen here in 2009) is a Midland Railway box dating from 1899, although the original mechanical lever frame has been replaced by electrical switches. (from Rail transport)
Image 32The Beijing Subway is one of the world's largest and busiest rapid transit networks. (from Transport)
Image 35The Great North Road near High gate on the approach to London before turnpiking. The highway was deeply rutted and spread onto adjoining land. (from Road transport)
Image 36Modes of road transport in Dublin, 1929 (from Road transport)
Image 37A prototype of a Ganz AC electric locomotive in Valtellina, Italy, 1901 (from Rail transport)
Image 38First powered and controlled flight by the Wright brothers, December 17, 1903 (from Aviation)
Image 42An ambulance from World War I (from Transport)
Image 43A cast iron fishbelly edge rail manufactured by Outram at the Butterley Company for the Cromford and High Peak Railway in 1831; these are smooth edge rails for wheels with flanges. (from Rail transport)
... that United States Secretary of Transportation Pete Buttigieg wrote an essay in 2000 on Bernie Sanders, his future competitor in the 2020 Democratic Party presidential primaries?
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