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Common Science 



FIG. 36. Why doesn't the water spill out? 



pail is starting down 

 behind you, the water 

 is tending to fly out in 

 the backward direction 

 in which it has just 

 been going. Therefore 

 it still pushes against 

 the bottom of the pail 

 and pulls away from 

 your shoulder, which is 

 in the center of the 

 circle about which the 

 pail is moving. By the 

 time you have swung 

 the pail on down, the 

 water in it tends to keep 



going down, and it is still pulling away from your 

 shoulder and pressing against the bottom of the pail. 



In this way, during every instant the water tends to 

 keep going in the direction in which it was going just 

 the instant before. The result is that the water keeps 

 pulling away from your shoulder as long as you keep 

 swinging it around. 



All whirling things tend to fly away from the center 

 about which they are turning. This is the law of centrif- 

 ugal force. The earth, for example, as it swings around 

 the sun, tends to fly away from the center of its orbit. 

 This tendency of the earth its centrifugal force 

 keeps it from being drawn into the sun by the powerful 

 pull of the sun's gravitation. At the same time it is 

 this gravitation of the sun that keeps the earth from 



