OfficialJasvirJassi/Shutterstock
When a round coin rolls down a聽slope, it stays upright, so why does聽a 鈥渟quare鈥 coin sliding down a聽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…
