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When a round coin rolls down a slope, it stays upright, so why does a “square” coin sliding down a slippery slope soon fall over?
Ron Dippold
San Diego, California, US
The round coin has two related advantages, rotational inertia and being a mini gyroscope.
Let us take the square coin first. If it is sliding down a slippery slope, narrow side leading, there is little to prevent it from tipping over. It is sitting on a narrow edge on a slippery surface, so it is inherently unstable. All it takes is the slightest variation in the slope to make…
