As I understand it:
Angle of repose refers to an object's lack of movement (friction) on an incline as compared to the angle of the incline.
Tipping point refers to balance of an object around/across its own center of mass.
... Let's just say that this evening's removal of the goat box from the back of the truck - which was already parked on an incline with the tailgate downslope - was an interesting practical lab exercise in various physical forces. One of those forces was the *lack* of friction between the bottom of the box and the truck's plastic bed-liner.
And totally unrelated: Son of Revenge of Sandwich Frog showed up on the front porch tonight. Hi!