LAWS OF MATTER 449 



where the moon attracted it with greater force than the earth; and 

 then it would be falling down toward the moon. 



Gravitation. Gravitation differs from gravity. Gravity means 

 the pull of the earth for all bodies on it. Gravitation means the force 

 which tends to draw all objects in the universe toward each other. 

 Large objects have a greater force of gravitation than small objects. 

 The sun, the moon, the planets and stars are all held in their position 

 by this great force of gravitation. 



Spherical Forms. Experiment. Fill a small bottle about half full of water. 

 Tip it gently. Fill the remaining part of the bottle with alcohol by allowing 

 the alcohol to run slowly down the side of the bottle so that it will not mix with 

 the water, but float on the surface. Drop a large drop of heavy oil into the 

 bottle. Since the oil is heavier than the alcohol, it will sink until it comes in 

 contact with the surface of the water. There sufficient alcohol and water 

 have mixed so that the bubble of oil will rest in the mixture. The bubble of 

 oil will assume a spherical shape. All material in a liquid form will assume a 

 spherical shape if allowed to act freely. 



Raindrops have a tendency to be spherical. Shot is manufac- 

 tured by allowing streams of molten lead to run through fine holes 

 from the top of a shot tower. These fine streams, before reaching 

 the bottom of the tower, break up into little balls of molten lead 

 which cool somewhat and harden before striking water at the bottom 

 of the tower. A splendid example of liquid breaking up into spheri- 

 cal forms may be seen by turning the faucet until only a fine stream 

 may be seen. Half way down the stream of water hundreds of 

 .little spheres of water are forming. 



QUESTIONS 



1. Why does one jumping from a height bend the knees on 

 alighting? 



2. In starting a load why does a horse have to give a harder 

 tug than he does to keep it moving after it is started? 



3. Why do we have great difficulty in stopping when running 

 down hill, especially when carrying a heavy weight? 



4. If the valve is suddenly closed after water has been running 

 .from the tap why will there be a noticeable thud? 



5. Why do automobiles skid when turning corners rapidly? 



