Stokes' law is most closely associated with which phenomenon in suspensions?

• A. Resistance to flow
• B. Color change
• C. Odor development
• D. Temperature dependence

Answer: (A)

Stokes' law describes the viscous drag a small sphere experiences as it moves through a fluid at low Reynolds number. The drag force, proportional to the fluid’s viscosity, the particle’s radius, and its velocity, represents the resistance to flow around the particle. In suspensions, this drag sets the terminal settling velocity under gravity, governing how quickly particles sediment and how stable the suspension is. So the phenomenon most closely linked to Stokes' law is the resistance to flow (viscous drag) in suspensions. Color change, odor development, and direct temperature dependence aren’t what this law primarily describes, though temperature can affect viscosity and thus drag indirectly.