APPLICATION 



163 



A along the incline ; but the smaller force must be applied 

 throughout the entire length of the incline. In many cases, 

 it is - preferable to exert a 

 force of 30 pounds, for ex- 

 ample, over the distance 

 CA than a force of 120 

 pounds over the shorter 

 distance BA. 



Prop the board so that 

 the end A is 2 feet above 

 the table level ; that is, ar- 

 range the inclined plane in 

 such a way that its length 

 is twice as great as its 



height. In that Case the FlG. 103. Primitive man tried to lighten his 



steady pull on the balance 



will be one half the weight of the roller; or a force of 6 



pounds will suffice to raise the 12-pound roller. 



The steeper the incline, the more force necessary to raise a 



weight; whereas if the incline is small, the necessary lifting 



force is greatly reduced. 

 On an inclined plane whose 

 length is ten times its 

 height, the lifting force is 

 reduced to one tenth the 

 weight of the load. The 

 advantage of an incline de- 

 pends upon the relative 



FIG. 104. Less force is required to raise the length and height, Or IS 

 roller along the incline than to raise it to A equal to the ratio Q f t h e 



directly. 



length to the height. 



156. Application. By the use of an inclined plank a strong 

 man can load the 6oo-pound bowlder on a wagon. Suppose 



