Gravitation 9 



Why fire engines are needed to force water high. In 

 putting out a fire, the firemen often want to throw the 

 water with a good deal of force. The tendency of the 

 water to seek its own level does not always give a high 

 enough or powerful enough stream from the fire hose; 

 so a fire engine is used to pump the water through the 

 hose, and the stream flows with much more force than 

 if it were not pumped. 



Application 2. A. C. Wheeler of Chicago bought a little 

 farm in Indiana, and had a windmill put up to supply the 

 place with water. But at first he was not sure where he 

 should put the tank into which the windmill was to pump the 

 water and from which the water should flow into the kitchen, 

 bathroom, and barn. The barn was on a knoll, so that its 

 floor was almost as high as the roof of the house. Which 

 would have been the best place for the tank : high up on 

 the windmill (which stood on the knoll by the barn), or the 

 basement of the house, or the attic of the house ? 



Application 3. A man was about to open a garage in San 

 Francisco. ,He had a large oil tank and wanted a simple 



FIG. 2. Where is the best location for the tank? 



