THE MECHANICAL POWERS. 287 



SOLUTION. 12 inches, length, : 3 inches, back, : : 200 Ibs., 

 resistance, : 50 Ibs. Ans. 



To find the requisite force when only one of the bodies is 

 movable. 



RULE. As the length of the wedge is to its back, so is 

 the resistance to the force. 



EXAMPLE. What power applied to the back of a wedge 

 will raise a weight of 20,000 Ibs.; the wedge being 6 inches 

 deep and 100 long on its base ? 



SOLUTION. 100 inches, length, : 6 inches, depth, :: 20,- 

 000 Ibs., weight, : 1200 Ibs. Ans. 



NOTE. The power of the wedge increases as its length 

 increases, or as the thickness of its back decreases. 



