578 Jonson — The Law of Dissipation of Motion. 



Akt. XXIV. — The Laiv of Dissipation of Motion; by 

 Erxst Jonsox. 



In order to explain the physical aspect of the universe 

 it is assumed that matter consists of separate particles 

 tied together by forces in such a manner that when the 

 particles move motion is transmitted from one particle 

 to another. Transmission of motion is mechanically con- 

 ceivable only if we assume that a force acts on the two 

 particles between which transmission of motion takes 

 place, i. e., when the two particles are the points of 

 application of a force. 



When two stars revolve about their common center of 

 gravity there occurs a continuous transmission of motion 

 from each one to the other. Such transmission of motion 

 involves permanent action of force. When a water mole- 

 cule collides with an iron molecule in the wall of a steam 

 cylinder the resulting transmission of motion is momen- 

 tary because the force acts only for an instant. The 

 revolution of masses of matter about each other is a 

 comparatively stable condition. Most natural changes 

 evidently are due to transmission of motion through col- 

 lision. In the mechanics of collision then must be found 

 the final explanation of all those natural phenomena 

 which result from the transmission of molecular energy. 



The following derivation of the Law of Dissipation of 

 Motion is a contribution to this branch of mechanics. 

 The chief immediate interest in this law arises from the 

 fact that it explains the Law of Dissipation of Energy 

 by rendering its mode of operation mechanically present- 

 able. 



When a collision occurs between two particles and the 

 motions of the colliding particles are not parallel, each 

 motion may be resolved into two perpendicular compon- 

 ents in such a way that each component of one motion is 

 parallel with one of the components of the other motion, 

 and so that the two components which have the same 

 direction also have the same size. The momentum AB 

 in figure 1 is resolved into the momenta AD and DB, and 

 the momentum CB into the momenta CD and DB. The 

 two coinciding components of the original motions repre- 

 sent the common motion of the two particles and have 

 therefore nothing to do with the collision. The collision 

 of the two particles results, of course, entirely from their 

 relative motion. This relative motion is represented by 



