6 4 



Common Science 



this extra motion at one 

 end more force is always 

 exerted at the other. 



This rule is true for all 

 kinds of levers, blocks 

 and tackles or pulley 

 systems, automobile and 

 bicycle gears, belt sys- 

 tems, cog systems, der- 

 ricks, crowbars, and every 

 kind of machine. In 

 most machines you either 

 put in more force than 

 you get out and gain mo- 

 tion, or you put in more 

 motion than you get out 

 and gain force. In the 

 following examples of the 

 lever see if you can tell whether you are applying more 

 force and obtaining more motion, or whether you are 

 putting in more motion and obtaining more force : 



Cracking nuts with a nut cracker. 



Beating eggs with a Dover egg beater. 



Going up a hill in an automobile on low gear. 



Speeding on high gear. 



Cutting cloth with the points of shears. 



Cutting near the angle of the shears. 



Turning a door knob. 



Picking up sugar with sugar tongs. 



Pinching your finger in the crack of a door on the hinge 

 side. 



FIG. 32. His hand goes down as far as 

 the pail goes up. 



