Why does one need to exert different amount of force when using the three classes of levers?
krishna-agrawala Teacher Graduate School eNotes Editor Lever is a simple machine which consists of a lever or a rod which swings around a fixed pivot called fulcrum. This mechanism provides a mechanical advantage in moving a load with effort that is less than the load. Lever makes it possible by changing the ratio of movement of the load and the effort. When an effort is applied directly to a load the length of movement of load and the effort is exactly same. But by using a lever it is possible to change this ratio. When the lever swings around its pivot the distance moved by different points on the lever is directly proportional to their distance from the fulcrum. The points nearer to the fulcrum move less and those away from the fulcrum move more. Points just on the fulcrum do not move at all. Therefore by changing the points on lever where load is placed and effort is applied and the position of the fulcrum it is possible to achieve different degrees of mechanical advantage. The exa