H2 ELEMENTARY SCIENCE 



Take the case of winding up a well-bucket on a wind- 

 lass (see page 55). Suppose the circumference of the cir- 

 cle described by the handle of the windlass when it is 

 turned is five times as great as the circumference of the 

 axle on which the rope is wound. Then, for each foot 

 that the bucket ascends, your hands pushing the handle 

 must move five feet. In other words, the work of lifting 

 the bucket one foot is distributed through a five-foot 

 effort, rather than concentrated in a one-foot effort, as it 

 would be if you pulled up straight. So it is just five times 

 as easy to push the handle one foot as it would be to pull 

 the bucket up one foot. It is just like breaking five sticks 

 one at a time instead of trying to break them all at once. 

 What you may not be able to accomplish by one great 

 effort, you can accomplish by a continuation of small effort, 

 and this in the end accomplishes as much as some stronger 

 person might be able to accomplish all at once. The 

 amount of work done is the same whether it be done all at 

 once or gradually, with the great advantage in favor of 

 the gradual method that it enables us to do things which 

 by direct methods we cannot do at all. 



Take the case of prying up a heavy stone with a stick 

 or a crowbar. In order to get a purchase you place a piece 

 of wood or stone under the crowbar, near the thing to be 

 pried up. The crowbar is a lever. The thing that gives 

 the purchase is the fulcrum. Now suppose it is one foot 

 from the fulcrum to your hands, and four inches from the 

 fulcrum to the thing you are prying up. Then for every 

 inch that the lower end of. the bar rises, your hands at the 

 other end must push down three inches. If you put all 

 your strength and weight on the end of the bar, and move 

 it down three inches, that strength and weight is multi- 



