EXAMPLES. 237 



EXAMPLES. 



1. A thin plane area moves edgeways through the water, 

 in which it is completely immersed. Find the resistance 

 per square foot at a speed of 20 miles per hour. 



Ans. 3.442 Ibs. 



2. The length of a pipe is 400 feet, the head of water is 

 6 feet, and the diameter of the pipe is 6 inches, the entrance 

 to it being cylindrical. Find (1) the head due to friction, 

 (2) the velocity of discharge, and (3) the quantity discharged 

 per second. 



Take / = 0.03, g = 32, and use (3) of Art. 104 for . 



Ans. (1) 5.646 ft. ; (2) 3.88 ft. ; (3) 0.7619 cu. ft. 



3. When the pipe is 800 feet long, the head of water 12 

 feet, and the diameter 6 inches, find (1) the friction head, 

 (2) the velocity of discharge, and (3) the quantity dis- 

 charged per second. 



Ans. (1) 11.635 ft. ; (2) 3.939 ft.; (3) 0.7734 cu. ft. 



4. When the pipe is 1600 feet long, the head 24 feet, and 

 the diameter 6 inches, find the same quantities as in the last 

 two examples. 



Ans. (1) 23.63 ft; (2) 3.969 ft. ; (3) 0.7793 cu. ft. 



5. When the pipe is 3200 feet long, the head 48 feet, and 

 the diameter 6 inches, find the same quantities. 



Ans. (1) 47.627 ft. ; (2) 3.984 ft. ; (3) 0.7823 cu. ft.* 



6. When the pipe is 800 feet long, the head 12 feet, and 

 the diameter 5 inches, find the same three quantities as 

 before. 



Ans. (1) 11.694 ft.; (2) 3.605 ft.; (3) 0.4915 cu. ft. 



* An inspection of Exs. 2. 3, 4, and 5, shows that if a 6-inch pipe be laid with a 

 uniform slope of 6 feet in 400 feet, nearly all the head is consumed by friction, so 

 that only a very small fraction of the entire head remains to generate the final veloc- 

 ity and to overcome the resistance at the entrance to the pipe, {. ., in each case 

 there is only abont 0.35 of a foot of head left ; one-third of this is expended in over- 

 coming the resistance at the entrance to the pipe, and the other two-thirds in pro- 

 ducing velocity. 



