SIMPLE MACHINES 



343 



times the power arm. The law applies just as well in the case 

 of bent levers as in those in which the weight arm and the power 

 arm form a straight line. The hammer is a good illustration 

 of the bent lever when it is used to pull a nail (Fig. 180). It 



FIG. 181. A wheelbarrow as a lever 



will be interesting to place the various levers seen in common 



mechanical devices in one or the other of these classes and to 



calculate whether one needs little or much power, as compared 



with the resistance 



overcome, to operate 



such devices. A few 



such contrivances may 



be mentioned; pupils 



will think of niany 



more: the lemon 



squeezer, wheelbarrow 



FIG. 182. Wheel and axle used in steering 

 a boat. 



(Fig. 181), scissors, 



nutcracker, crank of a 



wringer or coffee mill, the forearm when the fist is brought up to 



the shoulder, the pump handle, etc. 



The windlass, wheel and axle, and capstan are familiar 

 applications of the lever with which astonishing results may be 

 accomplished. Recently in Chicago, a large brick building, 



