SOME EFFECTS OF NEWTON'S LAWS 



53 



Experiment 46. Try to balance an egg on its end. Explain 

 the result (Fig. 34). Do the same with a weighted ball or disk 

 (Fig. 35). Hang a ball by a thread, as in Fig. 36, and move it 



Fm. 34 



FIG. 35 



to a position a. Now where is the e.g. of the whole pendulum? 

 Release the ball and note its behavior. When it comes to rest, 

 where is its center of gravity? 



63. The Problem of Support. When a body is fall- 

 ing freely its e.g. moves in a straight line 

 towards the center of the earth, nearly. \ 

 This straight line is called the line of 

 direction. Since gravity acts as if the \ 



force were applied along this line, a body \ 



will not fall so long as the straight line from 

 its e.g. to that of the earth passes through 

 its base, or point of support. 



c 



O 





Experiment 47. Find the e.g. of your ruler 

 by balancing, and mark the point. Now place ((T) 

 the ruler on a table, push it over the edge little FIG. 36 



by little, and note the position of its e.g. just before it falls. 



The base of a body is the area inclosed by straight 

 lines drawn from one to another of its outer points of 



