Incipient Motion Criteria for a Rigid Body on a Rigid Surface

Criteria for the incipient motion of a rigid body initially resting on a rigid surface are formulated from first principles in this work. The axiom that both body and surface are rigid allows for enormous simplification. A modified Coulomb friction model and an associated distribution of reaction forces are proposed. Incipient rotation and incipient translation are then considered as seperate categories of motion for the purposes of a more conventional approach. In this way a model which caters for the majority of combined translations and rotations is devised. Although incipient motion criteria could be thought of as the principles underlying a diverse spectrum of problems, they are developed here in the context of a model for sediment erosion. A sedimentation model which would largely be based on the probability of erosion (as defined empirically in terms of incipient motion criteria) is outlined.