Physics

Problem

For low-speed motion of a small sphere through a viscous fluid, the drag force

F

is found to depend on the sphere's radius

r

, its speed

v

, and the dynamic viscosity of the fluid

\eta

. Which proportionality satisfies dimensional requirements? a)

F \propto \eta r^{3} v^{-1}

F \propto \eta r^{2} v

F \propto \eta r v

F \propto \eta r v^{2}