Fluid statics- pressure intensity and hydrostatic force

[l.l.h]

Homework Statement

a concrete dam, 20m in height, has a vertical upstream face. if the water level is coincident with the top of the dame, calculate and plot the pressure intensity at 4m intervals over a vertical and thus determine the total hydrostatic force acting per unit width. Show that this force F, is equal to rho*g*h^2/2

Homework Equations

P=rho*g*h
P2=Patm+rho*g*h

The Attempt at a Solution

im okay calculating from the equation however i am unsure when calculating the pressure intensity do i consider the atmospheric pressure or not

 

[SteamKing]

Homework Statement

a concrete dam, 20m in height, has a vertical upstream face. if the water level is coincident with the top of the dame, calculate and plot the pressure intensity at 4m intervals over a vertical and thus determine the total hydrostatic force acting per unit width. Show that this force F, is equal to rho*g*h^2/2

Homework Equations

P=rho*g*h
P2=Patm+rho*g*h

The Attempt at a Solution

im okay calculating from the equation however i am unsure when calculating the pressure intensity do i consider the atmospheric pressure or not

I think you can safely assume that the downstream face of the dam is exposed to the atmosphere, thus, when asked to calculate the hydrostatic force per unit width, this force results from the water pressure alone acting on the upstream face of the dam.