In levers of the third order, the load is
placed at the end of the lever, and the muscle is attached somewhere
between the load and the fulcrum (Fig. 9 A). In the example we are
considering, the brachial muscle is attached about half an inch beyond
the fulcrum at the elbow, while the total length of the lever, measured
from the elbow to the palm, is 12 inches. Now, it is very evident that
the muscle or power being attached so close to the elbow, works under a
great disadvantage as regards strength. It could lift a 24-lb. weight
placed on the forearm directly over its attachment as easily as a single
pound weight placed on the palm. But, then, there is this advantage: the
1-lb. weight placed in the hand moves with twenty-four times the speed
of the 24-lb. weight situated near the elbow. What is lost in strength
is gained in speed. Whenever Nature wishes to move a light load quickly,
she employs levers of the third order.
[Illustration: Fig. 9A.--A chisel used as a lever of the third order. W,
weight; P, power; F, fulcrum.
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