THE MECHANICAL POWEKS. 



The mechanical powers are three in number, namely : 

 the LEVER, the INCLINED PLANE, and the PULLEY. The 

 wheel and the axle is a revolving lever ; the wedge is a 

 double inclined plane, and the screw is a revolving inclined 

 plane. 



THE LEVER. 



To find the length of the longest arm of the lever ; the 

 weight to be raised, the power to oe applied, and the length 

 of the shortest arm of the lever "being given. 



KULE. Multiply the weight by its distance from the ful- 

 crum and divide the product by the power, and the quotient 

 is the distance from the fulcrum the power must be applied, 

 or, the longest arm of the lever. 



EXAMPLE. Given, a weight of 900 Ibs., distant 2 feet from 

 the fulcrum, to be raised by a force or power of 75 Ibs. ; re- 

 quired, the length of the longest arm of the lever. 



SOLUTION. 900 Ibs., the weight, x 2 feet, distance from 

 fulcrum, =1800 -^75 Ibs., the power, =24 feet. Ans. 



To find the length of the shortest arm of the lever ; the 

 weight to "be raised, the power to "be applied^ and the length 

 of the longest arm of the lever being given. 



