A vertical rectangular steel door in a harbor wall is 2.0 m high and 1.2 m wide. The door is hinged along its top edge, which is located 5.0 m below the water surface. Experiments show that the resultant force of the water on the door acts at a point 1.3 m below the hinge line. Use ρsea water=1020kg/m3 and g=9.8m/s2.
(a) Calculate the gauge pressure at the top edge and at the bottom edge of the door.
(b) Determine the average gauge pressure acting on the door and hence compute the magnitude of the net force exerted by the water.
(c) Using the location of the resultant force given above, compute the torque about the hinge produced by the water.
(d) A horizontal handle is attached to the bottom edge of the door. Find the minimum horizontal force that must be applied at the handle to keep the door closed.