THE INCLINED PLANE. THE WEDGE. 



89 



required is 200 x 3 .= 600 kilogrammetres, the 

 necessary force therefore - - = 30 kgr . A road up a 

 hill, a flight of steps, two long poles used for rolling a 



FIG. 62 



real size). 



barrel up into a waggon, are familiar examples of the 

 application of an inclined plane. 



Very similar to the inclined plane is the wedge, fig. 

 63, used for splitting wood. 



The thin edge is inserted in a cut previously made 

 in the wood, and force being applied at 

 the back or broad end of the wedge, 

 either by pressure or a blow, the wedge 

 is driven onward through a certain space, 

 and the portions of wood on both sides 

 are further separated. If a wedge 25 cm 

 long and 5 cm broad is driven in, up to 

 the broad end, by a force of 100 kgr , the 

 space passed over will be 25 cm = O m '25, 

 and the work done 100 x 0*25 = 25 

 kilogrammetres. The portions of the log 

 are separated by 5 cm = O m> 05; this is the 

 space through which the resisting force has been over- 



25 



*' 



rC 



come ; this force is therefore 



0-05 



= 500 kgr . 



Most of our instruments for cutting, as knives, chisels, 

 have a wedge-shaped section, and their action is quite 

 similar to that of the wedge. 



