CHAPTER II. 



MEASUREMENTS : THE DYNAMIC ELEMENTS OF THE 

 HUMAN MACHINE. 



217. The Evaluation of Work. The dynamograph, if it is 

 arranged so as to indicate 

 the effort, and the dis- 

 placement at the point of 

 application of that effort, 

 is the proper instrument 

 to measure the work done. 

 Its graph shows the value 

 of the effort and the 

 amount of the displace- 



Q 



*S*J 



FIG. 101. 



ment at any moment. 

 Suppose the muscles pro- 

 duce a constant effort, represented by the ordinates^ ..., y n , in 

 n seconds, and displace the resistance opposing them by distances 



ox lf x^x.j ..., x n _^ K . The 

 the 

 sum 









total work done by 

 muscles will be the 

 of the products ox l x y 

 -f x x 2 x y 2 + ..., say ox 

 xy (fig. 191). If the effort 

 were variable, the total area 

 would be that of fig. 192. 



If the variation of the 



FIG. 192. 



effort is continuous, the graph would take the form of a curve C 

 (fig. 193) and the area to be found would be that of OAB*. 



Fio. 193. 



(R) 



Fio. 



Area of right-angled triangle. 



