I'm working on a problem, and I'm getting too muddled in trying to figure what is the normal force.
If the whole thing was at rest, the normal force would simply be the angled reaction for $mg$, but since an acceleration is acting on the system, I'm thinking it will "relieve" some of the normal force (i.e. act against the horizontal $mg$ force to lessen the amount that the normal force has to accommodate for [if that makes sense?]). But I think I'm getting confused because I have an acceleration to work with, not a force.
I finally cracked and peeked in the back of the book. Using the value it gives for $O_y$, it seems that the normal force should be 438.357N. This is assuming that $\Sigma F_y = 0 = -mg + N cos\theta + O_y$. But if I take the sum of the moments about O (which will eliminate $O_y$, $O_x$, and I'm thinking any force related to $a$?), I get that $2 mg cos \theta= N$, so then $N =$ 588.6N.
So I guess I'm officially confused... how does that normal force work with that acceleration at $O$?