To solve this problem we will begin by finding the pressure through density and average depth. Later we will find the Force, by means of the relation of the pressure and the area.
[tex]P = \rho h[/tex]
Here,
h = Depth average
[tex]\rho[/tex] = Density
Moreover,
[tex]\text{Density of water}= \rho = 62.4lb/ft^3[/tex]
Replacing,
[tex]P = (62.4lb/ft^3)(\frac{35}{2}ft)[/tex]
[tex]P = 1092 lb/ft^2[/tex]
Finally the force
[tex]\text{Force} = \text{Pressure}\times \text{Area of dam with water acting on it}[/tex]
[tex]F = 1092lb/ft^2(101ft*52ft)[/tex]
[tex]F = 5.735*10^6lbf[/tex]