250 



Our Surroundings 



The Wedge. The wedge is a combination of two inclined 

 planes. The longer the wedge the greater its mechanical advantage. 



The wedge is employed, 

 by means of blows on the 

 thick end, to split rocks, tim- 

 ber, and other objects difficult 

 to separate into parts by other 

 methods. Axes, hatchets, 

 knives, and other cutting in- 

 struments sloped on both sides 

 of the cutting edge are constructed on the principle of the wedge. 

 The Screw. The screw is an inclined plane wound round a 

 cylinder, thus making a circular inclined plane called the thread 



THE WEDGE 



A double inclined plane. 



APPLICATIONS OF THE INCLINED PLANE 



How is the inclined plane applied in each case? What other elementary machines 



do you see ? 



of the screw. The screw is used in combination with the lever in 

 moving large or heavy bodies through short distances. It is also 

 employed in presses of all kinds where considerable force is 

 needed, as in bookbinders' presses. Another illustration of the 

 screw is the automobile jack. 



