(3) To change a small, fast moving force into a powerful force, as in the action of a crowbar.
(4) To change the direction of a force so that the power can be applied where and when it is needed, and
(5) To make use of whatever force is at hand as the strength of animals, wind, water, steam, gas and electricity.
The Six Mechanical Powers.—As a matter of fact there are really only two of these, namely the lever and the inclined plane, the other four, that is the wheel and axle, the pulley, the wedge and the screw being simply modified forms of the first two.
Fig. 37a. A LEVER OF THE FIRST CLASS
Fig. 37b. A PAIR OF PLIERS
The lever is a rigid bar resting on, and which can be moved about a fixed point, called the fulcrum. There are three classes of levers and these are: