When should we use p = ρ.g.h and p = ρ.g.hcg for hydrostatic pressure?

AI Thread Summary
The discussion clarifies the appropriate use of the equations p = ρ.g.h and p = ρ.g.hcg for calculating hydrostatic pressure. The first equation is used when measuring pressure based on the height of the water column, while the second accounts for the distance to the center of gravity from the water surface. It emphasizes that h should be measured to the center of pressure, which may not align with the center of gravity for submerged bodies. Understanding these distinctions is crucial for accurate pressure calculations in fluid mechanics. Accurate application of these formulas is essential for effective engineering and design in fluid systems.
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For the hydrostatic pressure, when do we use [ p = ρ.g.h ] and [ p = ρ.g.hcg ]

where:
ρ = density
g = acc of gravity
h = height of water column
hcg = the distance to the center of gravity from the surface of water downward
 
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It depends. h should actually be measured from the surface to the 'center of pressure', which is not always located at the c.g. of a submerged body.

http://www.nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/FLUID-MECHANICS/lecture-5/5-2_hydro_thrust_plane_surf.htm
 
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