The pulley block is formed by matching several fixed pulleys and movable pulleys, which can save effort and change the direction of force. In use, the amount of effort saved and the winding method of the rope depend on the effect of the pulley block. The principle of rope winding is: when the number of fixed pulleys and movable pulleys are equal, the free end of the rope can come out of the movable pulley or the fixed pulley, and when coming out of the fixed pulley, the fixed end of the rope is hung on the fixed pulley; driven pulley When coming out, the fixed end of the rope is hung on the movable pulley. The difference in the number of fixed pulleys and movable pulleys shall not exceed 1. When the number of them is not equal, the free end of the rope comes out from the more side, and the fixed end of the rope hangs on the less side. When the movable pulley is fixed, when the fixed end of the rope is hung on the movable pulley, the pulley block is less effort than when the fixed end of the rope is hung on the fixed pulley (because there are more pieces of rope to bear the weight of the object).
Let n be the number of rope segments that bear the weight of the object (for example, the pulley set on the left side n=5, and the right side n=4), then the n-segment rope can be equipped with n or n-1 pulleys. When equipped with n wheels, the number of movable pulleys and fixed pulleys Equal, and the fixed end of the rope is on the fixed pulley; when n-1 pulleys are equipped, n is an odd number, and the fixed end of the rope is on the movable pulley.
When using a pulley block, a heavy object is supported by several ropes, and the force used to lift the object is a fraction of the weight of the object
