UNIFORM MOTION. 225 



water due to the resistance of friction must be equal to the 

 fall. The height due to the resistance of friction increases 



v 

 with , with the length /, and with the square of the ve- 



locity v (Art. 102). Hence, from (1) of Art. 103, we have 



in which / is an empirical number, which is called the coef 

 ficient of friction. 



Solving (1) for v, we have 



*$h* (2) 



According to Eytelwein's reduction of the ninety-one ob- 

 servations and experiments made by du Buat, Brunings, 

 Funk, and Woltmann, / = 0.007565, which in (1) gives 



h = 0.007565^- (3) 



a 2g 



If we put g 32.2 feet, (2) and (3) become 



, (4) 



h = 0.00011747 ^ v 2 . (5) 



For the number of cubic feet of water flowing through 

 the channel per second, we have 



Q = av = 92.26- (6) 



COB. For pipes, we have 



Ip _ fad _ 4? 

 ~a " -ncP ~~ d ' 



