 
Objective
In Part I, students will notice that the closer the fulcrum is to the load, the less force is required to lift the load. There is a point where the fulcrum is so close to the load that it appears no force is required at all. The weight of the lever itself (in this case, the ruler) is actually providing the needed force. This is one reason why crowbars are very heavy. In Part II, students should note that the position of the fulcrum also affects how far you push down and how far the load is lifted up. Levers trade force (how hard you push) for distance (how far you move the load). For example, when you apply a small force over a long distance, you move the load a small distance. Students should notice that when they use less force to lift the load, the distance they push the lever arm down is larger than the distance the load is lifted. When they use more force to lift the load, the distance they push the lever arm is smaller than the distance the load is lifted. When the fulcrum is placed in the middle of the lever, the distance the load is lifted is about equal to the distance that the other end of the lever is pushed down. In this situation there is essentially no mechanical advantage—the distance over which the force is applied equals the distance the load is lifted. 


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