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2 Early Work 3 Force and Levers 4 The Three Classes of Levers |
A lever is a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force that can be applied to another object. This is also termed mechanical advantage, and is one example of the principle of moments. The principle of leverage can also be derived using Newton's laws of motion and modern statics.
The earliest remaining writings regarding levers are provided by Archimedes ("Give me a place to stand, and I can move the Earth.", a remark of Archimedes quoted by Pappus of Alexandria) who formally stated the correct mathematical principle of levers.
The force applied (at end points of the lever) is proportional to the ratio of the length of the lever arm measured between the fulcrum and application point of the force applied at each end of the lever. (M=Fd)
The principle of the lever tells us that the above is in static equilibrium with all forces balancing. The force applied upwards on the boulder is equal to the ratio of the lever arms times the force applied downward at the other end. (40/2)*50 = 1000. By slightly increasing the downward force the boulder begins to move.
There are three classes of levers representing variations in the location of the fulcrum and the input and output forces.
Definition
Early Work
Force and Levers
An Example
Principle of the Lever
The Three Classes of Levers