This is an applied example for which the precritical path is nonlinear and stable. The postcritical path proves to be unstable, and hence one gets either collapse or snap-through. In the case of this example, there exists another stable equilibrium path for which the load can be increased further, and the solution snaps from the critical point, which proves to be a limit point, to another stable equilibrium branche.

The Lecture Slides

The equilibrium path on slide 4 is plotted wrongly for negative values of N. It should in principle be similar to the equilibrium paths plotted later in the lecture.