Having seen how
the head is moved as a lever of the first order, we are now to choose a
part which will show us the plan on which levers of the second order
work, and there are many reasons why we should select the foot. It is a
part which we are all familiar with; every day we can see it at rest and
in action. The foot, as we have already noted, serves as a lever in
walking. It is a bent or arched lever (Fig. 6); when we stand on one
foot, the whole weight of our body rests on the summit of the arch. We
are thus going to deal with a lever of a complex kind.
[Illustration: Fig. 5.--Showing a chisel used as a lever of the second
order.]
In using a chisel to pry open the lid of a box, we may use it as a lever
either of the first or of the second order. We have already seen (Fig.
1) that, in using it as a lever of the first order, we pushed the handle
downwards, while the bevelled end was raised, forcing open the lid. The
edge of the box served as a rest or fulcrum for the chisel. If, however,
after inserting the bevelled edge under the lid, we raise the handle
instead of depressing it, we change the chisel into a lever of the
second order.
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