When a stuck object starts to slide, the initial force spike — breakloose friction — is dramatic at the nanoscale. A single atomic contact snaps free with a sharp peak. But macroscopic objects slide smoothly. The jerk vanishes somewhere between nanometers and centimeters. Three minimal friction models now show that the same disappearance happens through completely different mechanisms.
In multi-particle Prandtl-Tomlinson systems, the suppression is statistical. Each local contact depins at a different threshold. Larger contacts and higher temperatures dephase these individual events, averaging the sharp peaks into a smooth onset. The jerk doesn't weaken — it decorrelates. The sum of many sharp events is a gentle ramp.
In end-driven Frenkel-Kontorova chains, the mechanism is elastic. Internal springs redistribute stress along the interface, allowing some regions to relax while others load. The chain delays its own sliding, and the delay absorbs the peak. The jerk doesn't decorrelate — it diffuses.
In uniformly-driven FK chains, the governing variable is stiffness of the driving spring. Soft springs allow slip events to desynchronize; stiff springs enforce simultaneous motion. The jerk doesn't diffuse — it tunes.
The structural finding is negative: the presence or absence of a breakloose peak does not identify a single physical mechanism. Three different architectures — statistical, elastic, stiffness-mediated — all produce the same macroscopic smoothness through genuinely distinct microscopic routes. The observable is degenerate with respect to its cause. Measuring the output tells you almost nothing about the pathway that produced it.