Forces on a Completely Submerged Gate

A gate hinged at the top is submerged under water. The gate is 2.5 meters long and 1 meter wide. This Demonstration calculates the force that must be applied 
to keep the gate closed. Use the sliders to set the water height and the gate weight. Check the "show distances" box to display distances.

Download the CDF file to view the simulation using the free Wolfram CDF player.