For exercise 4 I also modeled the hour glass for the first scene of my PSA. The aim of the exercise was to create an animation using cloners. So i took it in to my advantage to combine the PSA work and the exercise to create the animation above. I used dynamics for getting the spheres to fall down in a realistic way. I also used an attractor object to make sure the fallen particles dont move too far from the bottom center of the hour glass.
Screenshot of the scene file: