<P> The physical reason for this behaviour is that the liquid contains particles (such as clay) or large molecules (such as polymers) which have some kind of interaction, creating a weak solid structure, formerly known as a false body, and a certain amount of stress is required to break this structure . Once the structure has been broken, the particles move with the liquid under viscous forces . If the stress is removed, the particles associate again . </P> <P> The material is an elastic solid for shear stress τ (\ displaystyle \ tau), less than a critical value τ 0 (\ displaystyle \ tau _ (0)). Once the critical shear stress (or "yield stress") is exceeded, the material flows in such a way that the shear rate, ∂ u / ∂ y (as defined in the article on viscosity), is directly proportional to the amount by which the applied shear stress exceeds the yield stress: </P> <Dl> <Dd> ∂ u ∂ y = (0, τ <τ 0 (τ − τ 0) / μ ∞, τ ≥ τ 0 (\ displaystyle (\ frac (\ partial u) (\ partial y)) = (\ begin (cases) 0, & \ tau <\ tau _ (0) \ \ (\ tau - \ tau _ (0)) / \ mu _ (\ infty), & \ tau \ geq \ tau _ (0) \ end (cases))) </Dd> </Dl> <Dd> ∂ u ∂ y = (0, τ <τ 0 (τ − τ 0) / μ ∞, τ ≥ τ 0 (\ displaystyle (\ frac (\ partial u) (\ partial y)) = (\ begin (cases) 0, & \ tau <\ tau _ (0) \ \ (\ tau - \ tau _ (0)) / \ mu _ (\ infty), & \ tau \ geq \ tau _ (0) \ end (cases))) </Dd>

Which of the following is the best example of a bingham plastic quizlet