298 EXAMPLES. 



radius, find the depth of the bell, supposing the atmos- 

 pheric pressure to be 14.28 Ibs. to the square inch (h = 34). 

 Ans. From surface to surface 73.3 feet. 



28. There is a pump lifting water 29 feet high, the 

 diameter of its piston is 1 foot, the play of the piston is 3 

 feet, and the pump makes 10 strokes per minute ; (1) how 

 many gallons of water will be discharged per minute, and 

 (2) what is the pressure on the piston ? 



Ana. (1) 147 gals.; (2) 1420 Ibs. 



29. Water flowing through a trough, 2 feet wide and 1 

 foot deep, with a velocity of 10 feet per second falls upon 

 an overshot wheel 50 feet in diameter. Find (1) the part 

 of the fall operating by impulse ; (2) the maximum useful 

 work of the wheel, the efficiency being 0.70 ; and (3) the 

 number of revolutions the wheel makes per hour when 

 doing maximum work. 



Ans. (1) 1.55 feet ; (2) 43076.25 ft-lbs. per sec. ; (3) 

 114.59. 



30. Water is furnished to a breast-wheel at the rate of 

 20 cubic feet per second with a velocity of 8 feet. The fall 

 is 20 feet and the efficiency 0.75. What is the useful work 

 done by the wheel when the periphery has a velocity of 3, 

 4, and 5 feet per second respectively ?. (See Sch. 1, Art. 

 155). 



Ans. 19185.94; 19215.94; and 19185.9 ft. -Ibs. per sec. 

 respectively. 



31. What is the useful work done by an undershot 

 wheel, 40 feet in diameter, making 120 revolutions per 

 hour, the velocity of the water being 20 feet per second and 

 the area of the vanes being 1 square feet ? 



Ans. 1910 ft.-lbs. per second. 



32. What is the efficiency of a reaction wheel when the 

 water having a head of 16 feet, issues from the orifices with 

 a velocity of 45 feet per second ? Ans. 0.8254. 



