When a lever provides a mechanical advantage, our
input force is amplified. But that increase in force does come
at a cost, just as it does with all other simple machines. A
lever with a mechanical advantage of 2 allows us to move
the load using half the force it would take without the lever
but covering only half the distance (traveling at half the
speed).
The mechanical advantage of the lever depends on the
distances between the fulcrum, the load, and the effort.
The so-called law of the lever states that the mechanical
advantage of a lever is equal to de/dl
, where de is
the distance between the effort and the fulcrum, and dl
is the distance between the load and the fulcrum. For
example, for the lever shown in Figure 7-2, de (indicated by
the blue arrow) is 5 studs long, and dl
(indicated by the red
arrow) is 3 studs long. Therefore, the mechanical advantage
of this lever is 5/3, or 1.67. This means that in order to lift
1 kg of load 1 meter with this lever, we have to apply the