EXAMPLE. 173 



From (1) and (3) we have 



v 2 W 



work done on the body = W (v v^ 



ty *>9 



W 



Now if the water leaves the body, there will be more work 

 lost, i. e., the work remaining in the water will be lost ; 

 therefore we have 



W v 2 



work done on the body = [v 2 (v v ifls -- a*~ ^ 



y y 



= (v v.) v l - (5) 



COR. 1. If P denote the pressure of the water against 

 the body, then the work done on the body = Pv lt which 

 in (5) gives 



P=(v- Vl ) ^- (6) 



*7 



If the body is at rest, or v l = 0, (6) becomes 



P = f (7) 



COB. 2. Let a = the section of the pipe, and v = the 

 velocity due to the head of water h ; then W = 62.5av, 

 which in (7) gives 



P = 62.5a x 2h. (8) 



EXAMPLE. 



To find the work of a stream of water issuing from a 

 nozzle with a given velocity. 



Let v be the given velocity, a the area of the nozzle, and 

 w the weight of a cubic foot of water. Then the weight of 



