(Kelly of the Clue Crew demonstrates with a coffee can & an inclined plane.)  A ball of clay inside the can is enough to reposition the can's natural center of this, so the can rolls uphill
[DOC] [TLE] A Wheel and a Double Cone Climb Up an Inclined Plane [PAR] Center of gravity at work: A wheel and a double cone climb up an inclined plane 
by ...