THE ANIMAL AS A MACHINE. 



V. 



Since — = the height due the velocity the work 



is equal to that required to raise the body through the 

 difference of the two heights due the initial and the 

 final velocities, respectively. 



Where the motion of the machine or of the part 

 doing work is circular, the space traversed may be 

 measured by the angular motion a, multiplied by the 

 lever-arm, /, and their product, multiplied by the force, 



exerted, gives the measure of the work done. Thus : 



in which last expression n is the number of revolutions 

 made in the unit of time. 



These values are equivalent to the product of the 

 angular motion into the moment of the resistance. 



Work may also be measured, as in steam, air, gas, or 

 water pressure engines, by the product of the area of 

 piston, A, the mean intensity of pressure upon it, /, the 

 length of stroke of piston, /, and the number of strokes 

 made. Thus, 



when V is the volume of the working cyhnder multiplied 

 by the number of strokes ; in other words, the volume 

 traversed by the piston. 



Where the force acting, or the resistance, acts ob- 

 liquely to the path traversed, it is evident that only the 

 component in that path is to be considered. 



Diagrams exhibiting the amount of work done and 



U — Apln 

 = Aps 

 = pV, 



(II) 



