RAILROADS AND HIGHWAYS 



299 



will have to push with this force against the bowlder while it 

 moves over the entire length of the plank. 



Since work is equal to force multiplied by distance, the 

 man has done work represented by 400 X 8, or 3200. This 

 is exactly the amount of work which would have been neces- 

 sary to raise the bowlder directly. A man even of enormous 

 strength could not lift such a weight (1600 Ib.) even an inch 

 directly, but a strong man can furnish the smaller force (400) 

 over a distance of 8 feet; hence, while the machine does not 

 lessen the total amount of work required of a man, it creates 

 a new distribution of work and makes possible, and even easy, 

 results which otherwise would be impossible by human agency. 



Railroads and highways. The problem of the incline is 

 important to engineers who construct highways and lay rail- 

 road tracks. It requires tremendous force to pull a load up 



FIG. 165. A well-graded railroad bed. 



^rade, and most of us are familiar with the struggling horse and 

 the puffing locomotive. For this reason engineers, wherever 

 possible, level down the steep places, and reduce the strain as 

 far as possible. 



