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What is a Fulcrum?

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  • Written By: Licia Morrow
  • Edited By: Bronwyn Harris
  • Last Modified Date: 18 August 2014
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A fulcrum, or pivot point, is the area around which a lever turns. A lever is a hard length of material -- or a bar -- used to put out force or maintain weight at one end, while pressure is exerted on its second end. In other words, when force is placed on one end of a bar or handle, which turns on the third point, or fulcrum, force or weight is managed on the second point of the lever.

A good example of a lever and its accompanying pivot point is a child’s see-saw. The ends of the see-saw, where participants sit, would be considered points one and two. The fulcrum is the area in the middle upon which the lever balances. When one participant pushes his or her weight, the pivot point in the center supports the motion of the second point on the lever either raising or lowering.

For the example of the see-saw, a class one lever, the weight is more or less distributed evenly by the pivot point because it is generally placed in the middle of the lever. In other words, the fulcrum is in between the force applied to one end, or input effort, and the resulting force, or output load. However, this is not always the case in lever and fulcrum relationships.

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In a second class lever, for example, the input effort’s location is at one end of the bar, the pivot point is located 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 diving board in which one end of the board springs because the fulcrum is located at one end and the force placed on the lever comes from a human jumping up and down.

In third class levers, the output load is on one end, with the fulcrum on the other, and the input effort or force is at some point between these two. Brooms and baseball bats would be good examples of third class lever in which force is placed in the middle, with output load (sweeping or hitting) occurring on the opposite end of the pivot point.

Levers, and their accompanying fulcrums, are considered to be one of six simple machines. The idea behind this control of force is called leverage, which can be attributed to Newton’s Law of Motion.

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hanley79
Post 2

@Malka - Hmm, good question. I'm leaning toward a no on that question, myself. See, a fulcrum and lever basic machine is that type of machine because it involves a lever and fulcrum. The new styles of seesaw with the springs in the middle don't rely on a fulcrum to let the lever rock back and forth on top of it -- instead of the lever's position moving across the top of the fulcrum, the spring's bending to accommodate the way the lever's ends are moving. So I'd call it a slightly different kind of basic machine -- a lever and spring device instead of a lever and fulcrum. See what I mean?

Malka
Post 1

Okay, so a seesaw counts as a level type device with the middle acting as the fulcrum, right? So I'm really curious now...there are new styles of seesaw that feature bendy springs in the middle instead of a hinge or traditional bump for the seesaw to bend up and down over. Do those still count as fulcrums because they're the spot underneath the lever that supports it as it moves?

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