I'l \ 



If in the dkgnun we drew from the origin (which need not be the same 

 point of pM W the origin for the material system) a vector equal :m<l 

 llrl to the vector which determines the position of the particle, the t-nd 

 thw twctor will indicate the position of the particle in the digram ..f 



If this done for all the particles, we shall have a system of points in 

 the diagram of configumtion, each of which corresponds to a particle of the 

 material system, and the relative positions of any pair of these points will In- 

 the mate as the relative positions of the material particles which correspond 



to them. 



We have hitherto spoken of two origins or points from which the vectoti 

 are supposed to be drawn one for the material system, the other for tin- 

 diagram. These point*, however, and the vectors drawn from them, may now 

 be omitted, so that we have on the one hand the material system ami <>n 

 the other a set of points, each point corresponding to a particle of the system. 

 and the whole representing the configuration of the system at a given instant. 



This is called a diagram of configuration. 



Diagram of Displacement. 



Let us next consider two diagrams of configuration of the same system, 

 corresponding to two different instants. 



We call the first the initial configuration and the second the final con- 

 figuration, and the passage from the one configuration to the other we call the 

 displacement of the system. We do not at present consider the length of 

 time during which the displacement was effected, nor the intermediate stages 

 through which it passed, but only the final result a change of configuration. 

 To study this change we construct a diagram of displacement. 



Let A, B, C be the points in the initial diagram of configuration, and 

 .V. It'. C 1 be the corresponding points in the final diagram of configuration. 



From o, the origin of the diagram of displacement, draw a vector on 

 fjual and parallel to A A', oh equal and parallel to BB', oc to CC', and so on. 



The ].ints. o, h, c, &c., will be such that the vector ab indicates tin- 

 displacement of I* relative to a, and so on. The diagram containing the points 

 , 6, c, Ac., is therefore called the diagram of displacement. 



In constructing the diagram of displacement we have hitherto assumed 

 that we know the absolute displacements of the points of the system. For 



