THE WEDGE. 



109 



PULLEY. 



DEFINITION. 



f FIXED. 

 KINDS. <! MOVABLE. 



[ COMBINATIONS. 



LAW. 



RELATION between the number of pulleys and the 

 number of parts of the cord. 



( DEFINITION. 



INCLINED ] FORCE OF GRAVITY 

 PLANE, j RESOLVED. 



IV. 



THE WEDGE, SCREW, COMPOUND MACHINES, AND 

 FRICTION. 



2O5. What is a Wedge? A wedge is a mov- 

 able inclined, plane in 

 which the power gener- 

 ally acts parallel to the 

 base. 



2O6. Its Use. This 

 wedge is used for moving 

 great weights short dis- 

 tances. The law is the FlG - 58. 

 same as for the corresponding inclined plane. A common 

 method of moving bodies is to place two similar wedges, 

 with their sharp edges overlapping, under the load. 

 Simultaneous blows of equal force are 

 struck upon the heads of the wedges. 

 In this case, the same force must be 

 used upon each wedge as if only one 

 FIG. 59. were used, but the power being doubled 



