effort needed to lift 0.6 kg and move the end of the lever
1.67 meters. The mechanical advantage still benefits us
because we’re trading time, which we have plenty of, for
force, which is limited.
The law of the lever also means that the force applied
to the arm of a lever is inversely proportional to the arm’s
length. Therefore, it takes more force to move a lever with
a short arm than it takes to move a lever with a longer arm.
A lever with a 3-stud-long arm will take twice the force
as a lever with a 6-stud-long arm to move the same load.
The lever with the 6-stud-long arm, though, will move the
load twice as far because of its longer length.
Figure 7-3 illustrates the distance/force proportion.
We have a lever with a 3-stud-long arm and a 7-stud-long
arm. If we apply force to the longer arm, the lever offers a
mechanical advantage of 2.33 (7/3), and if we apply force
to the shorter arm, the lever offers a mechanical advantage
of 0.43 (3/7). If we put a 1 kg load on the longer arm and a
2.33 kg load on the shorter arm, the loads will balance each
other.
Note that a lever can have equal de and dl
distances,
resulting in a mechanical advantage of 1. This simply means
that there is no mechanical advantage and the distance/force
balance remains unaltered. Such a lever can still be useful,
as it reverses the direction of movement (that is, by pushing
down, you lift a load up).
Finally, note that a lever does not necessarily have to
be a straight beam. It can be bent and work just the same.
A simple crowbar is a good example of a bent lever (see
Figure 7-4): It has a long arm, a short arm, and a central