Chap. XLI.] LEVERS. 495 



its distance from F to be 2 feet, its moment = 20. 

 Now let the distance between F and p = 5 feet, a 

 force of 4 pounds will give a moment of 20. Thus 

 with these distances a force of 4 pounds at P will 

 balance a force of 10 pounds at w. If p be made 

 5 pounds its moment will exceed that of w, and 

 will pull the bar 

 down towards it ; w 

 will be raised. The 

 smaller weight acting 

 through the longer 

 distance will raise 



the heavier weight. Fi S- 204.-Lever of the First Order. 



The power and weight 



are in the inverse ratio to their arms. There are 

 three classes of levers, according to the relative posi- 

 tions of P, w, and F, the power, weight, and fulcrum. 

 That which has been already described is a lever of 

 the first order, where the fulcrum is between the 

 power and the weight. Its advantage is that a small 



power may be made 

 to raise a very heavy 

 weight if the arms of 

 the lever are properly 

 adjusted. But it is 

 apparent that the 



1 12. 205. Lever of Second Older. 



power must travel 



through a very considerable distance to raise a heavy 

 weight even, a small amount. This is well shown in 



O 



Fig. 204, where the weight w is raised only a short 

 distance, while the power performs a considerable 

 excursion from P to P'. One great advantage evident 

 from Fig. 203 is that by this lever two forces may 

 readily be balanced by adjusting the position of F. 



Fig. 205 represents a lever of the second order, 

 where the weight is between the power and the fulcrum. 

 In it the power always acts through a longer arm 



