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jbriggs444
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Not at all. Quite the opposite. Without friction, the perpendicular orientation is an equilibrium point regardless of curvature. With friction, it is (almost certainly) not. We agree on that.Baluncore said:You seem to be assuming there is some friction present at the contact patch.
If one is to consider stability, the curvature of the surface near the contact point becomes relevant, even without friction. Both a needle and a bopping buddy are in equilibrium in a perpendicular orientation. The needle is unstable at that equilibrium. The bopping buddy is stable there.
A single coin in a "perpendicular" orientation (flat on its face) will be in a stable equilibrium with or without friction [barring a rather extreme slope and coefficient of friction].