Common Science 



FIG. 26. The little girl raises the big boy, but in doing it she moves twice as 

 far as he does. 



nearer the middle. Why should it matter where the 

 larger child sits ? He is always heavier why doesn't 

 he overbalance the small child ? It is because when the 

 small child moves up and down he goes a longer distance 

 than the large child does. In Figure 26 the large boy 

 moves up and down only half as far as the little girl does. 

 She weighs only half as much as he, yet she balances 

 him. 



You will begin to get a general understanding of levers 

 and how they work by doing the following experiment : 



Experiment 18. For this experiment there will be needed 

 a small pail filled with something heavy (sand or stones will 

 do), a yardstick with a hole through the middle and another 

 hole near one end and with notches cut here and there along 

 the edge, and a post or table corner with a heavy nail driven 

 into it to within an inch of the head. The holes in the yard- 

 stick must be large enough to let the head of this nail through. 



Put the middle hole of the yardstick over the nail, as is 



