Ayya, that minimum speed is √(gR) at the very top, so the roller coaster doesn't fall off the tracks. That √(5gR) you hear? It's the speed needed *at the bottom* to make it all the way up and just barely reach that top speed—it comes from adding up the energy for the whole loop.
But I'll tell you, these formulas forget the grip and the grit. I've seen boys in my gym, thin as ropes, use sheer momentum to pull themselves over the bar where the math said they'd fail.
It's like my old Bullet motorcycle—sometimes the feeling in your hands tells you more than the speedometer ever could.
#middle-distance#5000m
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