Why do dust particles settle down on the floor in a closed room? Explain.

(N/A) Dust particles can be modeled as small spheres moving through the air. According to $Stoke's$ $Law$, the viscous drag force acting on a spherical particle is $F = 6\pi\eta rv$. As the particle falls, it reaches a $terminal$ $velocity$ $(v_t)$, which is given by $v_t = \frac{2r^2(\rho - \sigma)g}{9\eta}$. Since the radius $(r)$ of dust particles is very small, their terminal velocity is extremely low. However, because this velocity is non-zero and directed downwards, the particles continue to move towards the floor. Over a period of time, even with a very small terminal velocity, these particles eventually settle down on the floor.