They don't tip over on hills for the same reason you don' tipover on hills. They adjust their balance with the muscles in their legs to lean up the hill just as humans do.
yes, because there is a potential that he'll move on that hill and his energy is stored while standing.
yes i think he is DANCING COWS
Gravity. Walking is a series of falls, to fall up a hill you must cheat a bit - by leaning forward.
Butte
She shifts her weight to the two legs that are uphill to the rest of her body. For example, if is standing perpendicular to the slope of a hill, her weight would be resting on the two legs that are more uphill than the other two. If she were standing downhill, her backlegs would be taking most of her weight. When she would shift her weight to the two feet that are more down hill from her, she will most definitely fall down.
Potential energy is the energy stored in a rock before its fall from a hill.
According to Turkey Hill's own website the cows are apparently "13 feet" but it doesn't say if that is length or height. It does mention that each of the cows weigh two tons.
The Parthenon
Climb a hill, and jump off it. If gravity exists you will fall down.
Gravitational potential energy.
Fall down a steep hill
try to climb a sandy mountain you will fall down