170 



MECHANICS 



when you cut cloth or use a nutcracker. Where" is the 

 easiest cutting done, near the fulcrum or at the tip of the 

 scissors? If you want to crack a hard nut where in the 

 nutcracker do you place it? The lever is called a ma- 

 chine since it enables man to use a small force to over- 

 come a large force. It is the simplest machine we have 

 and has been known for countless centuries. See Sec- 

 tion 80. 



66. The Inclined Plane, 



Another machine which is very simple and has been 

 known as long as, if not longer than, the lever is the 

 inclined plane. This is simply a board with one end 

 higher than the other. Instead of lifting a weight verti- 

 cally it is pushed or rolled up the slanting board. Since 

 the force acts a longer distance up the plane it is not as 

 great as it would be if it acted only vertically. How is 

 this like the lever? 



Experiment 72. Tile Use of the Inclined Plane. 



Apparatus: As 

 shown in the 

 illustration, rule. 



a. Find the 

 weight of the car 

 with its load of 

 stones or weights. 

 Find the force 

 3 which i s neces- 

 sary to pull the car up the inclined plane. Which is 

 greater? 



