450 RECAPITULATION. 



2. As the diameters of circles are in proportion 

 to their circumferences, the power is to the weight 

 also as the diameters. 



3. If one wheel move another of equal circum- 

 ference, they will both move equally fast. 



4. But if a wheel move another of different 

 diameter, whether larger or smaller, the velocities 

 with which they move will be inversely as their 

 diameters, circumferences, or number of teeth. 



Pulley. 



1. Pullies are of two kinds, fixed and ynoveable. 



2. In the fixed pulley, when the power and 

 weight are equal, they balance each other, and no 

 mechanical advantage is obtained. 



3. In the moveable pulley, the power need only 

 to be equal to half the weight, to balance. 



Inclined Plane. 



That the power and weight may balance each 

 other, the former must be to the latter as the 

 height of the plane to the length. 



Wedge. 



1 . When the resistance acts perpendicularly to 

 the sides, the power will be to the weight as half 

 the thickness of the wedge on the back is to the 

 length of the sides. 



2, When the resistance acts parallel to the back, 

 the power is to the resistance as the whole length 

 of the back to that of the sides. 



