WATER PRESSURE 



125 



removed and the pipe filled with water, the pressure upon 

 the water in the pipe, tending to force it out, would be also 

 0.434 pound; that is, the pressure would be equal to the 

 weight of water directly above the hole. The width or length 

 of the tank has nothing to do with this. The pressure de- 

 pends on the area and the depth of the water but not upon 

 any other feature of the tank. 



140. Effect of the shape of a tank. Since, as we have found, 

 the pressure on any area may be found by the use of only three 

 factors, the area, the depth of 



the liquid, and the weight of unit 

 volume of the liquid, the shape 

 of the vessel can have nothing to 

 do with the pressure. This can be 

 easily shown by experiments with 

 a variety of apparatus, and these 

 experiments should be performed 

 in the laboratory. 



141. Pressure in other liquids. If 

 any other liquid than water (petro- 

 leum, for example) is to be stored 

 or handled, the problems of pres- 

 sure are precisely the same as in 

 the case of water, excepting that 

 the weight of the liquid will be dif- 

 ferent, and therefore in solving problems concerning it we 

 must ascertain its weight per cubic foot or cubic inch and use 

 this quantity as our weight per unit volume. 



142. Calculation of fluid pressure. It will be sufficient if 

 we remember that to calculate any liquid pressure we must 

 take area X depth X weight of unit volume. 



If the English units are employed, the unit of weight may 

 be either ounce, pound, or ton, but the same unit must be 

 used throughout any given calculation. In the metric system 

 the solution of problems is much more easily accomplished. 



FIG. 66. Pressure in a pipe 



The dimensions of the tank, ex- 

 cepting its depth, do not affect 

 the pressure in the pipe 



