A pulley is a wheel on an axle or shaft enabling a taut cable or belt passing over the wheel to move and change direction, or transfer power between itself and a shaft.
A pulley may have a groove or grooves between flanges around its circumference to locate the cable or belt. The drive element of a pulley system can be a rope, cable, belt, or chain.
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Cable transport is a broad class of transport modes that have cables. They transport passengers and goods, often in vehicles called cable cars. The cable may be driven or passive, and items may be moved by pulling, sliding, sailing, or by drives within the object being moved on cableways. The use of pulleys and balancing of loads moving up and down are common elements of cable transport. They are often used in mountainous areas where cable haulage can overcome large differences in elevation.
Telescoping in mechanics describes the movement of one part sliding out from another, lengthening an object (such as a telescope or the lift arm of an aerial work platform) from its rest state. Manually extended telescoping devices are common in modern products, for example they are used in umbrellas, selfie sticks, pop up canopy shelters, and (to extend handles) luggage. In heavy equipment, extension can be achieved by a hydraulics, but pulleys are generally used for simpler designs such as extendable ladders and amateur radio antennas.