Hydrostatic Force Problem - Calculus

HanRam
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Homework Statement


Find hydrostatic force on the vertical side of the tank that has the shape of the region bounded by the curves y=2x2, y=8. Assume that the tank is full of water.

Homework Equations


F=pgAd (force = density*gravity*area*depth)

The Attempt at a Solution


I know I need to set up and evaluate an integral, and I believe it must be evaluated from 0 to 8, since the top of the tank is at y=8. Other than this though, I have been unable to set up the integral that I need. Any help as to how the integral would be set up would be appreciated.
 
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After hours working at this problem, I think I may have figured it out, but I'm not at all sure that I did it correctly. Anyway, here is what I came up with.

\int(1000)(9.8)(8-2x^2)(2x)dx

After calculating this integral from 0 to 2 (I did this because x=0 corresponds to the bottom, and x=2 corresponds to the top), I multiplied my result by 2 to compensate for the fact that I was only integrating for the right side (0 to 2), and by multiplying by 2, that would cover the left side (-2 to 0).

My final result was 313600 N. Can anybody tell me if I went wrong somewhere? (Which I have a feeling I did).
 
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I'll give you 10 dollars for a typed response. 10 dollars. Anybody want to make 10 dollars and respond virtually? No?
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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