Kinetic Friction by a Small Number of Intervening Inelastic Particles between Rough Surfaces

TL;DR

This study models granular friction by analyzing a minimal system of inelastic particles between rough surfaces, revealing that mutual collisions induce a nonzero average resistance force, thus demonstrating a fundamental mechanism for kinetic friction.

Contribution

It introduces a simple dynamical model with a small number of particles to explain the emergence of kinetic friction through mutual collisions.

Findings

Resistance force scales with pulling velocity

Average resistance force remains nonzero as velocity approaches zero

Mutual collisions between particles cause kinetic friction

Abstract

We investigate a mechanism of the appearance of kinetic friction in granular materials. We consider a small number of intervening inelastic particles between two rough surfaces as one of the simplest dynamical models to study granular friction. The resistance force applied to the upper surface is numerically calculated. We find that the resistance force F(t) is scaled as F'(vt) for a small pulling velocity v. The time average F_0=<F(t)> in the limit v->0 is not zero owing to the mutual collisions between the intervening particles. The nonzero F_0 implies the appearance of kinetic friction in this simple dynamical system.