Levers

Levers are one of the basic tools; they were probably used in prehistoric times. Levers were first described about 260 BC by Archimedes. Many of our basic tools use levers, including scissors (two class-1 levers), pliers (two class-1 levers), hammer claws (one class-1 lever), nutcrackers (two class-2 levers), and tongs (two class-3 levers). The lever consists of three elements: the place where force is applied, the load to be moved, and the pivot point or fulcrum. These can be arranged in various orders. The familiar situation of pushing down on a beam to lift a load has the elements in the order force- fulcrum-load. A wheelbarrow is a lever with its elements in the order force-load-fulcrum (the wheel is the fulcrum). The lever was still amazing enough that in the third century B.C. Archimedes could awe listeners by saying "give me a place to stand and a lever long enough, and I will move the Earth".