 A pulley is a grooved wheel that turns on an axle. The groove in he wheel causes the rope or cable to ride on the wheel without slipping off.The pulley is generally used to assist lifting heavy weights. 1. The pulley can change the direction of a pull. In this case, pulling down on the rope will lift the weight up. With just one pulley as shown below there is no saving of effort, but it provides a way to maneuver the weight more conveniently. 2. With the pulley arrangement shown below, less effort is required. Half the weight is supported by the overhead beam, and half is supported by the person holding the other end of the rope. The weight is shared so the human effort is less. However, now the rope will have to be pulled twice the distance. You would have to use half as much force to lift the weight, but you would have to pull the rope twice as far, as compared to the first example shown above. |
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