I'ROl'KKTV OF EQflLIIIIl! .".I . 



iiistt*'fiil in Static* 



force* oci .menu zero for certain 



is an important general pro- 

 position to * iplo leads. 



Jus under the action of no faro 

 jtrcMurf*, and pressure* upon tmoodt 

 tmmoveaole *urfuct* t will be tn ay 



fAt o0fi/Tt 'A foiMrt or highest position it can 



possibly consul 



nexion of its parts with one another. 



incea below a fixed horizontal 

 liflerent particle* of the ^ 

 ese particles. That the system may I 

 libnom, we must nave 



...-0. I); 



it* of all the other forces 

 i act on the system vanish. Let 

 the centre of gravity of the system below the fixed horizontal 



:ore 10+ v-f w+ ... oj - 



:ore 10^+ v t -f w t + ... oj - ^oir, -f tr t o> t -h 

 v when * has a maximum or minimum value, 



..... (S), 

 (see Di/. Cole. Arts. 232, 238). 



ice, when the centre of gravity is at a Tp^ximnm or 

 minimum distance from the fixed horizontal plane, (1) is 

 satisfied and the system is in equilibrium. 



:i (3) is a necessary but not a sufficient con- 



niving a maximum or minimum value ; hence, 



we cannot assert conversely, th the system is in 



entre of gravity must be at a maximum or 



:num de; 



It the system of rigid bodies be such that the centre of 

 same horizontal plane, every position 



