110 GENERAL THEOREMS. [CHAP. VI. 113 



Observing that it is a consequence of the Law of internal 

 action (Article 106) that the system X , Y , Z is equivalent to 

 zero, and operating as in Article 107, we can deduce equations 

 which may be stated in words : 



The change of momentum of the particle G in any direction is 

 equal to the sum of the resolved parts of the external impulses in 

 that direction. 



The change of the moment of momentum of the system about 

 any axis is equal to the sum of the moments of the external 

 impulses about that axis. 



