The conditions for stability If object rests on 1 point, then that point must lie vertically below center of mass, and the radii of curvature of the surface at that point, must exceed the distance to the center of mass. If object rests on 2 points A,B (or line segment AB) then the center of mass must be vertically above the line segment, and the max radius of curvature of the surface at the contact points in directions perp to the line AB, must exceed the distance to the center of mass. If object rests on 3 or more noncollinear points then the center of mass must be vertically above a point interior to their convex hull (if above a hull-boundary point then use the 2-point condition). -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)