70 



APPLIED SCIENCE 



20" > 



2ft. 



of the liquid, whose base and length are respectively the area 

 of that portion of the side and its average depth. This may 

 be explained in another way. The pressure against the 

 vertical side of a tank at the surface of the water is zero, 

 for the liquid has no depth. But the pressure on the side 

 increases with the depth until we reach the bottom of the 

 tank, when it is equal to the pressure against the bottom. 

 The average pressure on the side then 

 is the pressure exerted on the middle 

 of the side, and is equal to one-half 

 the pressure per unit of surface 

 against the bottom. 



The following laws apply to 

 liquids : 



I. The pressure does not depend 

 upon the size or shape of the vessel. 

 The pressure increases with the verti- 

 cal depth below the free surface. 



II. At any point in a liquid, the 

 upward, downward, and lateral or 

 sideways pressures are equal. 



III. To find the lateral pressure of 

 Fir,. 42. Tank of Water, water, upon the sides of a tank, multi- 

 ply the area of the submerged portion 



of the side in inches, by the pressure of one-half the depth. 



As an example: What is the lateral pressure on one side of a 

 tank 20 in. wide and 2 ft. deep (Fig. 42)? The solution is as follows: 

 20 in. X 24 in. = 480 sq. in., area of side. 

 2 ft. X .434 = .868 lb., pressure at bottom of tank. 

 .868 -s- 2 = v434 lb., average pressure due to one-half the 



depth of tank. 

 .434 X 480 = 208.32 Ibs., pressure on one side of the tank. 



(Copyrighted by Millers Falls 



