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Now assuming the wind is stopped by the wall, the pressure of the wind at a given height is [itex]P=\frac{Force_{on small area,dA}}{dA}=\frac{mass per second_{hitting area,dA} v_{wind speed}}{dA}=\frac{\rho_{air}vdA v}{dA}=\rho v^2 = \rho v_0^2 h^2/4[/itex]

Now to find the total force of the wind, I would integrate the pressure with respect to the area, and since the width of the wall w is constant, this turns out to be

[itex]\int_{0}^{2}Pwdh =\rho w v_0^2/4 \int_{0}^{2}h^2dh[/itex]

But then for the moment about the lowest edge of the wall wedged into the ground, it would be [itex]\int_{0.7}^{2.7}Fdh[/itex] but the force is an integral of h because it is pressure x w x dh, so how do I deal with integrating with respect to h twice? Could someone please explain the principles behind this as well because I am really trying to improve my skills in applying calculus...

Note: I realise that this sounds like a homework question, but it is not. It is just something I was thinking about and trying to fiddle with myself. If it would be better suited to the homework thread though, I would be happy to move it, it's just that my main question is about applied calculus methods rather than just finding an answer to a question :)