ANS:B - force on a vetical projection of the curved surface

The horizontal component of the force on a curved surface is equal to the force on a vertical projection of the curved surface. This principle is based on the laws of fluid mechanics, specifically the hydrostatic pressure distribution over a curved surface submerged in a fluid. When a curved surface is submerged in a fluid, the pressure distribution varies across the surface. The pressure at any point on the curved surface depends on the depth of the fluid at that point and the curvature of the surface. To determine the total force exerted on the curved surface, we need to integrate the pressure distribution over the entire surface. The horizontal component of this force is equal to the force that would be exerted on the vertical projection of the curved surface. This concept is often applied in engineering calculations involving fluid mechanics, such as the analysis of submerged surfaces, buoyancy, and hydrostatic forces. Therefore, the correct statement is: force on a vertical projection of the curved surface.