MECHANICAL WORK. 77 



ever, somewhat different in the experiments made with 

 the machine for demonstrating the motion of falling 

 bodies. The wheel and weights were not moved by their 

 whole weight, but by the extra weight placed to the 

 right. In the first experiment (page 51), we had on the 

 left side 72 gr , on the right 74 gr , that is an extra weight of 

 2 gr or O kgr '002. The weight of 2 grammes acts through 

 a perpendicular distance of 2 decimetres or O m *2. The 

 accumulated work is, therefore, O002 x 0*2 = 0'0004 

 kilogrammetres. This can be proved by observing the 

 motion which takes place after the extra weight has 

 struck upon the perforated plate. A weight of 4^ is 

 thus removed on the right side, and there is now an 

 extra weight of 2 gr on the left side ; nevertheless, the 

 weight on the right side continues to descend through 

 a further space of nearly 2 decimetres. By the work 

 accumulated in the moving mass (wheel and weights), a 

 weight of O kgr< 002 is raised through nearly O m> 2, that is, 

 work is done amounting nearly to O0004 kilogram- 

 metres. The reason why the work done is not exactly 

 0'0004 kilogrammetres is that a weight of 4^ was 

 retained upon the plate, and the accumulated work of 



remainder only could be used for doing work. 

 The height to which a body rises, if projected with a 

 r en velocity, or, as it is called, ' the height due to 

 locity/ is, as shown in the preceding article, found by 

 r iding the square of the velocity by twice the accelera- 

 >n of gravity. A moving body is capable of raising 

 ts own weight to this height ; that is, it is capable of 

 loirig an amount of work which is equal to the product 

 )f its weight into the height due to its velocity. It follows 

 .hat : 



