A vertical dike retains 18m of water. It is pierced at its base with a semi-circular door of 4m in diameter (the base of the gate is its diameter), as in the drawing below. The hydrostatic force exerted by the water on the portion of the door between y and y+delta y is approximately p(y)delta y. What is p(y)? density rho=1000kg/m^3; g=9,8m/s^2. What is the total hydrostatic force acting on the door?

Une digue verticale retient 18 m d'eau. Elle est percee a sa base d'une porte semi-circulaire de 4 m de diametre (la base de la porte est son diametre), comme sur le dessin ci-dessous. porte --t- O