286 THE MECHANICAL POWERS. 



NOTE. It will be observed that, according to the above 

 rules, illustrated by the foregoing examples, the power or 

 force of traction and the weight or load are equivalents ; 

 that is to say, the one is, by the interposition of the wheel 

 and axle, made to counterpoise the other. To find their 

 easy practical value, deduct J from the weight, or add to 

 the tractile force. 



THE WEDGE. 



To jmd the force necessary to separate two bodies from 

 one another in a direction parallel to the ~back of ike wedge. 



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

 is the resistance to the force. 



EXAMPLE. The length of the back of a double wedge is 

 6 inches, and its length through the middle 12 inches. Re- 

 quired, the force necessary to separate a substance having a 

 resistance of 200 Ibs. ? 



