# Stokes' Law

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Stokes' law, abbreviated as St, is the force that is put on a small sphere, slowing down the movement through a viscous fluid.

## Stokes' law formula

 $$\large{ F = 6 \; \pi \; r \; n \; v }$$

### Where:

 Units English Metric $$\large{ F }$$ = force $$\large{ lbf }$$ $$\large{N}$$ $$\large{ \pi }$$ = Pi $$\large{3.141 592 653 ...}$$ $$\large{ r }$$ = radius of sphere $$\large{ ft }$$ $$\large{ m }$$ $$\large{ v }$$ = velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ $$\large{ n }$$ = viscosity $$\large{\frac{lbf-sec}{ft^2}}$$ $$\large{\frac{m}{s}}$$

Tags: Force Equations