Basic hydrostatic equation for Pressure field Rectangular free body P+↓↑ of top area a W P+ dP Body of fluid in equilibrium ∑F,=0 PA+W=(P+ dP).A .A+pgadh=(P+ dP)a dP/dh=pg=y dP/dy =-pg-YBasic Hydrostatic Equation for Pressure Field Body of fluid in equilibrium :  Fy = 0 P.A + W = (P + dP) . A P.A +  g A dh = (P + dP) A dP/dh =  g =  dP/dy = -  g = -   h dh P P + dP W Rectangular free body of top area A y