Gravitation 



21 



winds. Naturally, if the air is pressing harder in one 

 place than in another, the lower air will be pushed 



FIG. 10. 



sidewise in the areas of high pressure and will rush to 

 the areas where there is less pressure. And air rushing 

 from one place to another is called wind. 



Application 4. A man had two water reservoirs, which 

 stood at the same level, one on each side of a hill. The 

 hill between them was about 50 feet high. One reservoir 

 was full, and the other was empty. He wanted to get 

 some of the water from the full reservoir into the empty 

 one. He did not have a pump to force the water from 

 one to the other, but he did have a long hose, and could have 

 bought more. His hose was long enough to reach over the 

 top of the hill, but not long enough to go around it. Could 

 he have siphoned the water from one reservoir to the 

 other? Would he have had to buy more hose? 



Application 5. Two boys were out hiking and were very 

 thirsty. They came to a deserted farm and found a deep 

 well ; it was about 40 feet down to the water. They had 

 no pump, but there was a piece of hose about 50 feet long. 

 One boy suggested that they drop one end of the hose down 

 to the water and suck the water up, but the other said that 

 that would not work the only way would be to lower the 

 hose into the water, close the upper end, pull the hose out 

 and let the water pour out of the lower end of the hose 

 into their mouths. A stranger came past while the boys 



