When a body is submerged in water, it experiences fluid pressure acting normal on its surface and distributed over its area. For better design structures, it is crucial to determine the magnitude and location of the resultant force acting on the surface. In the case of a rectangular plate of constant width submerged in water, the pressure increases with depth, resulting in a linearly varying trapezoidal pressure distribution from the upper to the lower edge of the plate.

The resultant force acting on this plate is due to the trapezoidal volume of water having a specific weight. The line of action of the resultant force passes through the centroid of this volume. The intersection of this line of action with the plate is referred to as the center of pressure, a significant factor affecting the stability and performance of the structure.

Due to the fixed width of the plate, the loading distribution can be represented efficiently in two dimensions. It makes it possible to express the resultant force acting on the entire plate as the product of the trapezoidal area and the width of the plate. This calculation enables efficient design and engineering of submerged structures, including ship hulls, docks, dams, and other hydraulic and civil engineering projects.

In conclusion, studying the fluid pressure acting on a flat plate of fixed width submerged in water is significant in designing submerged structures. The pressure distribution created due to the water pressure can be represented by the equivalent loading in two dimensions, and knowledge of the resultant force acting on the plate is essential for ensuring the stability and performance of the structure.