π€ Predict first β how many spins?
Why?
π‘ Watch the teal stick. It stays perpendicular to the ground, like a flagpole riding along. The purple arrow spins past the stick exactly the rolling number of times. The stick's own turning is the bend part β that's the extra (or missing) spin.
The rule: spins = (track length Γ· coin circumference) Β± bend.
Outside a circle: R/r + 1 Β· Inside: R/r β 1 Β· Straight road: Β±0