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Examples of rope and pulley systems illustrating mechanical advantage. Consider lifting a weight with rope and pulleys. A rope looped through a pulley attached to a fixed spot, e.g. a barn roof rafter, and attached to the weight is called a single pulley. It has a mechanical advantage (MA) = 1 (assuming frictionless bearings in the pulley ...
A fixed pulley changes the direction of the force on a rope or belt that moves along its circumference. Mechanical advantage is gained by combining a fixed pulley with a movable pulley or another fixed pulley of a different diameter. Movable: A movable pulley has an axle in a movable block. A single movable pulley is supported by two parts of ...
A block and tackle [1] [2] or only tackle [3] is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift heavy loads.. The pulleys are assembled to form blocks and then blocks are paired so that one is fixed and one moves with the load.
Belts are looped over pulleys and may have a twist between the pulleys, and the shafts need not be parallel. In a two pulley system, the belt can either drive the pulleys normally in one direction (the same if on parallel shafts), or the belt may be crossed, so that the direction of the driven shaft is reversed (the opposite direction to the ...
A dumb pulley can lift very large masses a short distance. It consists of two fixed pulleys of unequal radii that are attached to each other and rotate together, a single pulley bearing the load, and an endless rope looped around the pulleys. To avoid slippage, the rope is usually replaced by a chain, and the connected pulleys by sprockets.
In a belt drive system, idlers are often used to alter the path of the belt, where a direct path would be impractical.. Idler pulleys are also often used to press against the back of a pulley in order to increase the wrap angle (and thus contact area) of a belt against the working pulleys, increasing the force-transfer capacity.
Case in point: Many of the season's hottest deals are expected to sell out before your leftovers have even cooled down. Take, for example, these AirPods Pro, which are down to the lowest price of ...
Movable type: The polymath scientist and official Shen Kuo (1031–1095) of the Song dynasty (960–1279) was the first to describe the process of movable type printing in his Dream Pool Essays of 1088. He attributed the innovation of reusable fired clay characters to a little-known artisan named Bi Sheng (990–1051).