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A pulley is a simple machine made with a rope, belt or
chain wrapped around a wheel. The pulley is usually used to lift a heavy object, which is called a load. There are three types
of pulleys, the fixed pulley, the movable pulley and the combined pulley. The fixed pulley is the only pulley
that when used individually, uses more effort than the load to lift the load from the ground. The fixed pulley when attached
to an unmovable object, for example,a ceiling or wall, acts as a first class lever with the fulcrum being located at the axis
but with a minor change, the bar becomes a rope.The advantage of the fixed pulley is that you do not have to pull or push
the pulley up and down. The disadvantage is that you have to apply more effort than the load. The movable pulley is a pulley
that moves with the load. The movable pulley allows the effort to be less than the weight of the load. The movable pulley
also acts as a second class lever. The load is between the fulcrum and the effort. The main disadvantage of a movable pulley
is that you have to pull or push the pulley up or down. The main advantage of a movable pulley is that you use less
effort to pull the load. Finally the combined pulley makes life easier as the effort needed to lift the load is less than
half the weight of the load. The main advantage of this pulley is that the amount of effort is less than
half of the load. The main disadvantage is it travels a very long distance.
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