i am stuck on this problem. can anyone show me how to do it?
By similar triangles, the width of the plate, in feet, at a depth of
$\displaystyle h(x)=(3+x) \;\ ft$
$\displaystyle \frac{w(x)}{10}=\frac{x}{4}$
$\displaystyle w(x)=\frac{5}{2}x$
$\displaystyle F=\int_{a}^{b}{\rho}h(x)w(x)dx=\int_{0}^{4}(30)(3+ x)(\frac{5}{2}x)dx$