K* PRESSURE OF A LIQUID At A.\T DEPTH. 



or, pa = gpaz (since F=z); (6) 



' P = HP*- (?) 



COR. 2. If A be the area of the base of a vessel, h its 

 height, and P the whole pressure on the base, we have, 



from (6), 



P = gphA. (8) 



That is, the pressure of a liquid on any horizontal 

 area is equal to the weigh t of a column of the liquid 

 whose base is equal to the area, and ivhose height is 

 equal to the height of the surface of the liquid above 

 the area. 



It is evidently immaterial whether the surface pressed is 

 that of the base of the vessel or a horizontal surface of an 

 immersed solid. 



COR. 3. Since the weight of a cubic foot of water = 1000 

 ozs. = 62.5 Ibs., we have, for the pressure on the bottom 

 of any vessel containing water, 



P = 62.5hA Ibs., (9) 



where h is the height in feet of the surface of the water 

 above the base, and A the area of the base in square feet. 



COR. 4. The pressure on the base of any vessel is 

 independent of the form of the vessel. 



Thus, if a hollow cone, vertex upwards, be filled with 

 water, and if r be the radius of the base and h the height 

 of the cone, we have for the pressure on the base, 



. P = gp-rrr^h [from (8)], 

 or, P = GS.Srrr 3 /* [from (9)] ; 



that is, the pressure on the base is the same as if the cone 

 were a cylinder of liquid of the same base and height as the 



