Procedure: Students are introduced to the terms “fulcrum”, “effort,”
and “load,” and asked to identify these points on several of their devices. Using
the
Sorting Mechanisms Worksheet they then sort the mechanisms from “What is a
Mechanism?” according to the arrangement of the effort, fulcrum and load:
effort-fulcrum-load (1st class lever); effort-load-fulcrum (2nd class lever); or
load-effort-fulcrum (3rd class lever).
“Input” and “output” are general terms that could be used with any system. A
special language is used in describing the most basic type of mechanism, the lever.
The input is often called the effort, and the output is called the load. As with
the terms “input” and “output,” both the “effort” and “load” could describe either
a force or a location.
In addition to the effort and the load points, every lever has a pivot that allows
the rest of the device to rotate. In the language of levers, the pivot is called
the fulcrum. Several important characteristics of lever operation depend on the
arrangement of the three elements: fulcrum, effort and load. There are three
different possibilities, labeled as first-, second- and third-class levers
below.
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