44 EXAMPLES. 



10. Find the height of the vessel in Ex. 9 so that the 

 pressure on the side may be equal to the pressure on the 

 bottom. 



Ans. The height must equal the radius of the base. 



11. The pressure on a square inch of surface in a vessel 

 of mercury is 1000 grains. Find the pressure on a circular 

 surface of one-quarter inch radius, placed 9 in. lower down, 

 mercury being 13.5 times as heavy as water. 



Ans. Pressure = 0.8886 Ibs. 



12. The water in a canal lock rises to a height of 18 ft. 

 against a gate whose breadth is 11 ft. Find the total press- 

 ure against the gate. Ans. Pressure = 49 tons.* 



13. The upper side of a sluice-gate is 10 ft. beneath the 

 surface ; its dimensions are 3 ft. vertical by 18 in. horizon- 

 tal. Find the pressure upon it. 



Ans. Pressure = 1 tons.* 



14. A dyke to shut out the sea is 200 yards long, and is 

 built in courses of masonry one foot high ; the water rises 

 against it to a height of 6 fathoms. Find the pressure 

 against the 1st, 18th, and 36th courses. 



{1st pressure = 610.4 tons.* 

 2d pressure = 318.1 tons. 

 3d pressure = 8.6 tons. 



15. Find the pressure, in pounds, of a cylinder of water 

 4 inches in diameter and 45 ft. in height. 



Ans. Pressure = 244.8 Ibs. 



16. A cubical vessel, each side of which is 10 ft., is filled 

 with water, and a tube 32 ft. long is fitted to an aperture in 

 it, whose area is one square inch. If the tube be vertical, 

 and of the same size as the aperture, and filled with water, 

 find the pressure on the interior surface of the vessel, (1) 

 neglecting the weight of the water it contains, (2) when the 

 weight of the water is taken into account. 



Ans. (1) 1,200,000 Ibs. ; (2) 1,387,500 Ibs. 



One ton = 2a0 Ibe. 



