306 



THE HUMAN MOTOR 



is the product of 1 kilogramme of weight displaced per metre 

 covered, horizontally or on a slope. This unit will be known as 

 the metre-kilogramme (symbol : Mkg.). 



When it is only a question of lifting a weight to the top of a 

 staircase of height H, the work done will be P X H, because the 

 subject really lifts his weight, exerting an effort P in the direction 

 of the displacement H. 



If he mounts a ladder, H will be the vertical distance in relation 

 to the ground, and not the length of the ladder. 



But according to the speed of the ascent, the subject will 

 expend an effort greater than P, so that the muscular work is 

 greater than the mechanical work. 



When the subject descends from a height, H, the mechanical 

 work due to the action of gravity on his total weight, P, is ob- 

 viously P X H. The muscular work done depends on the effort 

 exerted in resisting the force of gravity. (See the following 

 chapter). 



233. Various Work due to the Muscles of the Legs. The tread- 

 mill or quarrier's windlass (fig. 216) is used to lift stones. It 

 comprises a wheel having steps projecting laterally around its cir- 

 cumference. The labourer 



climbs these steps, and 

 thus works it by his 

 weight acting at the ex- 

 tremity of a very long 

 radius R. The work done 

 per revolution is : 



T = 2rR x P. 



The ascension is in this 

 case virtual, the subject 

 not really mounting at 

 all. 



In working the treadle 

 of a sewing machine or a 

 grindstone, (which are 

 levers of the third order) 

 the experimental shoe will 

 give the value of the 

 effort. The effort varies 

 according to the hardness 

 of the material to be 

 worked, the pressure of 

 the tool on the stone, etc. 



234. The Complexity of Industrial Labour. The analysis of 

 the methods of measurement has necessitated a classification by 



Fio. 216. 



Treadmill or quarrier's windlass. 



