Pi from Block Collisions
Two frictionless elastic blocks. Count the collisions.
With mass ratio 100, you get 31.
With 10,000 you get 314. The blocks are counting π.
100
π ≈
Velocity space — the hidden circle
P1: M/m = 100 → exactly 31 collisions
P2: M/m = 10,000 → exactly 314 collisions