56 GENERAL SCIENCE 



Experiment 12. Pierce a meter stick in the center and balance it 

 on a nail as shown in Figure 47. By means of a thread suspend a 

 200-g. weight at A, 20 cm. from the point of support, the fulcrum. 

 Hang a 100-g. weight on the other arm of the lever and move it until 

 the bar just balances. It will be found that the 100-g. weight is 40 cm. 

 from the fulcrum. 



Wxd = Fxd' 

 200x20 = 100x40 



Perform the experiment with other weights at different distances 

 from the fulcrum. Does the law hold in every case ? 



Classes of Levers. There are three classes of levers 

 depending upon the relative location of the 'power, the 

 fulcrum, and the weight. In the lever of the first class 

 (Figure 48), the fulcrum is placed between the weight and 



FIG. 48. Lever of the First Class. 



the power. Scissors, weighing balances, pump handles, 

 and crowbars are examples of this class of lever. 



In the lever of the second class (Figure 49) the weight 

 is between the fulcrum and the power. The nutcracker 



IP ' 



FIG. 49. Lever of the Second Class. 



and the wheelbarrow are levers of the second class. In 

 the nutcracker the hinge is the fulcrum, the nut is the 

 weight, and the force applied to the handles is the power. 



