I'm probably going a bit ahead of myself messing with Physics, but I like getting my hands dirty. :)

I opened one of the included scenes in Carrara 8 Pro which shows a ring falling on a checkered plain.

I want to see the same forces acting on a sphere, and aiming to have like a rubber bouncing ball effect.

So I added the sphere and comparing the attributes of the Ring I changed the settings of the ball to match the ring.

When I play the animation.  The ring falls and rolls around but the ball just sits there.

I looked at the down force object and didnt notice how it was linked to the ring.

This is the same problem I'm having with stacking objects and having them fall apart.

Also, once I started playing with the physics parameters of the sphere.  It just got stuck in mid air.  I couldnt move it.