248 EFFLUX OF MOVING AIR. 



and this must equal the work done by the expansion of the 

 air from p t to p z . Therefore, from (2) of Art. 128, we 

 have 



The volume of air passing through the pipe per second is 

 !#!, and that which passes the orifice is a s v z ; hence we 

 have (Art. 48) 



a \p\ 

 which in (1) and reducing, gives 



. = / -= -^=> (2) 



which is the velocity of efflux. 



COR. Substituting for the numerator its value as given 

 in (8) of Art. 129, we have 



1 __ I ^2 J g I 



or approximately, whenjt?, is not much greater than p s , 





IKY 



\aj 



