MASS AND WEIGHT 



19 



the mass of the body. The weight of the body is the re- 

 sult of the earth's pull upon the mass of the body. If, in 

 some way, the pull upon a given body is increased, the 

 weight will be in- 

 creased; but if the 

 pull is weakened, the 

 weight will be de- 

 creased. Now, how 

 can we change the 

 effect of gravity, that 

 is, the attraction of 

 the earth for a cer- 

 tain mass? We can 

 do it by changing the 

 distance between the 

 earth and the body. 

 In other words, the 

 attraction between 

 two bodies depends 

 not only on their 

 masses, but also on the distance they are apart. The 

 distance between two bodies is taken to be the distance 

 between their centers. 



Suppose we have two balls weighing, say, 1 ounce each, and 1 inch 

 apart. If we place them 2 inches apart, the force of the attraction be- 

 tween them will be only 34 as great as at 1 inch. If the distance be- 

 tween them is made ^ an inch, the attraction will be 4 times what it 

 was originally. Now, we have learned that the earth is not a perfect 

 sphere, but is flattened at the poles. An object at the poles is about 13 

 miles nearer the earth's center than if it were at the equator. As a 

 result of this difference a body weighing 589 pounds at the equator 

 would weigh 590 pounds at the poles. 



Copyright International Stereograph Co., Decatur, 111. 



Fio. 15. 

 Leaning Tower of Pisa. 



