1 64 MAN^S WAY OF HELPING HIMSELF 



the floor of the wagon is 2 feet above the ground, then if a 

 6-foot plank is used, 200 pounds of force will suffice to raise 

 the bowlder ; but the man 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 200 x 6, or 1200. This 

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

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

 strength could not lift such a weight (600 Ib.) even an inch 

 directly, but a strong man can furnish the smaller force (200) 

 over a distance of 6 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. 



157. Railroads and Highways. The problem of the incline 

 is an important one to engineers who have under their direc- 

 tion the construction of our highways and the laying of our 

 railroad tracks. It requires tremendous force to pull a load 



FIG. 105. A well-graded railroad bed. 



