A flat plate of area 0.15 m² slides at a steady 0.60 m/s over a fixed surface, on a film of oil 1.2…

Viscosity: the force to slide a plate of area $A$ at speed $v$ over a film of thickness $d$ is $F = \eta A\dfrac{v}{d}$. Stokes' law: a small sphere feels $6\pi\eta rv$, so it falls at a terminal speed $v_t = \dfrac{2r^2(\rho - \sigma)g}{9\eta}$.