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andyrk
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When we say "pulley is frictionless", do we mean its groove where the string moves or its axle or both?
mfb said:The axle - but if you can neglect kinetic energy of the wheel, a frictionless groove gives the same result.
That's not what mfb wrote. mfb said that (frictionless axle with massless wheel) gives the same result (i.e. no role in the equations) as frictionless groove.andyrk said:How? How does it give the same result as an axle which has friction, if we neglect KE of the wheel?
A pulley is a simple machine that consists of a wheel with a groove around its circumference and a rope or belt that runs through the groove. It is used to change the direction of the force needed to lift an object.
There are three main types of pulleys: fixed, movable, and compound. Fixed pulleys have a stationary axle and are used to change the direction of the force. Movable pulleys have a freely moving axle and are used to multiply the force applied. Compound pulleys combine fixed and movable pulleys to both change the direction and multiply the force.
The two main conditions for pulleys to work effectively are having a stable support for the pulley and having a taut rope or belt running through the pulley. The pulley should also be properly sized and aligned to prevent friction and maximize efficiency.
The mechanical advantage of a pulley is calculated by dividing the output force (the weight being lifted) by the input force (the force applied to the rope or belt). This ratio can also be expressed as the number of rope segments supporting the weight.
Pulleys are commonly used in lifting and hoisting systems, such as in elevators and cranes. They are also used in transportation systems, such as in bicycles and cars. Pulleys can also be found in exercise equipment, window blinds, and many other everyday objects.