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A fulcrum is the point around which a lever rotates. Levers are used to exert force or hold weight at one end, while pressure is exerted on the other. There are three types of levers: first-class, second-class, and third-class. Levers and fulcrums are considered one of the six simple machines and are based on Newton’s law of motion.
A fulcrum, or pivot point, is the area around which a lever rotates. A lever is a piece of hard material – or a bar – used to exert force or hold weight at one end, while pressure is exerted on its other end. In other words, when force is placed on one end of a rod or handle, which pivots on the third point, or fulcrum, the force or weight is applied to the second point of the lever.
A good example of a lever and its pivot point is a child’s swing. The ends of the swing, where the participants sit, would be considered points one and two. The fulcrum is the area in the center on which the lever balances. As a participant pushes his or her weight, the pivot point in the center supports the movement of the second point on the lever as it moves up or down.
For the seesaw example, a class one lever, the weight is more or less evenly distributed from the pivot point because it is generally placed in the center of the lever. In other words, the fulcrum is between the force applied to one end, or input effort, and the resultant force, or output load. However, this is not always the case in leverage and fulcrum relationships.
In a second-class lever, for example, the input force location is at one end of the bar, the pivot point is at the other end of the bar, and the output load is between these two forces. A good example of a second class lever is a trampoline where one end of the board moves because the fulcrum is at one end and the force placed on the lever comes from a man jumping up and down.
In third-class levers, the output load is on one side, with the fulcrum on the other, and the input effort or force is somewhere between these two. Brooms and baseball bats would be good examples of a third class lever where the force is placed in the middle, with the output load (sweeping or striking) occurring at the opposite end of the pivot point.
Levers and their fulcrums are considered one of the six simple machines. The idea behind this force control is called leverage, which can be attributed to Newton’s law of motion.
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