30 Common Science 



All architects and engineers and builders have to take 

 this law into consideration or the structures they put 

 up would topple over. And your body learned the law 

 when you were a little over a year old, or you never 

 could have walked. It is worth while for your brain 

 to know it, too, because it is a very practical law that 

 you can use in your everyday life. 



If you wish to understand why the Leaning Tower 

 of Pisa does not fall over, why it is hard to walk on 

 stilts, why a boat tips when a person stands up in it, 

 why blocks fall when you build too high with them, and 

 how to keep things from tipping over, do the following 

 experiment and read the explanation that follows it: 



Experiment 12. l Unscrew the bell from a doorbell or a 

 telephone. You will not harm it at all, and you can put it 

 back after the experiment. Cut a sheet of heavy wrapping 

 paper or light-weight cardboard about 5X9 inches. Roll 

 this so as to make a cylinder about 5 inches high and as big 

 around as the bell. Hold it in shape by pasting it or putting 

 a couple of rubber bands around it. Cut two strips of paper 

 about an inch wide and 8 inches long; lay these crosswise; 

 lay the bell, round side down, on the center of the cross. 

 Push a paper fastener through the hole in the bell (the kind 

 shown in Figure 14) and through the crossed 

 pieces of paper, spreading the fastener out so 

 as to fasten the paper cross to the rounded 

 side of the bell. Bend the arms of the cross 

 up around the bell and paste them to the 

 sides of the paper cylinder so that the bell 

 makes a curved bottom to the cylinder, as 

 FIG. 14. shown in Figure 15. 



f To THE TEACHER. If you have a laboratory, it is well to have this 

 cylinder already made for the use of all classes. 



