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I was observing a construction work this morning. A kind of bulldozer was moving things on the ground and the dust waves (?)/clouds were illuminated by the sun behind.

From my POV it seems that the dust is flying in some pretty complex motion, but seems like a motion with a constant speed. And strikingly different than, let say, water droplets.

schematic depiction of particle motion

As I see it, some air "resistance" force (probably, I'm missing the right English term here) of an equal to gravity value is applied to the dust particle.

So, suppose the complex turbulent air motion around the particle is absent, but the air resistance is present, how high would a dust particle go, if expelled from the ground in the vertical direction?

I mean, since we know that dust eventually settles down, what is the mechanism that brings the dust back? Is it a decreasing air density, that influences the air resistance?

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  • $\begingroup$ It depends upon the size of each dust grain. Some grains are large enough to move ballistically through the air, others are small enough to obey fluid dynamics like diffusion and convection. I suppose there is a finite probability that a small enough dust grain could diffuse slowly up to high levels in the atmosphere but I am guessing for something like a single bulldozer, this probability is small. $\endgroup$
    – honeste_vivere
    Commented Oct 1, 2020 at 16:59

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