There is a gate in a dam. The upper edge of the gate runs along the water surface. The gate is 2 m high and 4 m wide and is hinged along a horizontal line through its center. I have to calculate the torque about the hinge arising from the force due to the water. I know how to calculate torque and water pressure with depth but I have no clue about this problem, I got a clue that tells me to calculate the torque of a thin horizontal strip at a depth h and integrate this over the gate, how should I do that. If someone has a clue, please help me.