Levers and linkages are some of the simplest machines and
form the basis for countless more complex mechanisms.
While levers are mostly used to provide a mechanical ad
vantage that allows us to move heavy loads, linkages are
mostly used to transform one type of a motion into another.
Both are common in everyday life: If you have ever played
on a seesaw or used pliers, you have relied on levers and
linkages.
levers
A basic lever is simply a beam that has one point of support
in the form of a hinge or a pivot, as shown in Figure 7-1.
We will call this point a fulcrum. A lever also has input and
output forces. We will call the applied, or input, force the
effort and the reaction force the load. Finally, we will call the
sections of the lever between its fulcrum and its ends arms.