6 Simple Machines

As you probably know, there are 6 simple machines:

1) Lever

2) Pulley

3) Wheel and Axle

4) Inclined Plane

5) Wedge

6) Screw

In the nineteenth century, the German mechanical engineer Franz Reuleaux (1829 - 1905) postulated that the 6 simple machines could be placed into 2 groups:

    Ⅰ) the lever, the pulley and the wheel and axle
      The "lever family" is grouped together because they function around a central point:
      the fulcrum, the pulley axis and the axle.

    Ⅱ) the inclined plane, the wedge and the screw
      The "inclined plane family" is grouped together because they function using angles.

A simple machine is something that can change the direction of a force, change the magnitude (amount) of a force or both.

In a simple machine, effort is the unchanged force (or input force) and load is the changed force (or output force).

When a simple machine changes the magnitude of a force, you are gaining what is known as a mechanical advantage, which equals the output force divided by the input force.

So, for example, if you are pressing fifty pounds on a lever to move a 200 pound boulder you have a mechanical advantage of 4. (200 ÷ 50 = 4)

output force ÷ input force = mechanical advantage

The important thing to remember about simple machines is that you do NOT get something for nothing.
You do get 200 pounds of force by only exerting 50 pounds of force, but moving the boulder ¼ of a foot (3 inches), requires moving the lever one foot.
Still, even though the lever doesn't give you something for nothing, it does make moving the boulder possible.

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