What manner of science makes ....
Discussion
dust stay on your car when you are travelling at motorway speeds?
Travelling at 100 leptons would mean, I suppose, that the wind travelling across your car is at least at hurricane speed, no? How the hell do the tiny specs of dust stay where they are then? I mean, if you are standing in such a strong wind you are seriously in danger of being lifted off your feet and thrown no small distance, yes? The winds that cross the Sahara reshape the landscape on a constant basis. Sand, lots of it, lifted and moved around. What manner of friction enables the smaller-than-sand flecks of dust to remain on the car? In the case of my own car the answer is easy...dirt has encased the dust and holds it there simply to remind me that the annual brush up is due!
Any scientists out there who could explain this phenomenon?
Travelling at 100 leptons would mean, I suppose, that the wind travelling across your car is at least at hurricane speed, no? How the hell do the tiny specs of dust stay where they are then? I mean, if you are standing in such a strong wind you are seriously in danger of being lifted off your feet and thrown no small distance, yes? The winds that cross the Sahara reshape the landscape on a constant basis. Sand, lots of it, lifted and moved around. What manner of friction enables the smaller-than-sand flecks of dust to remain on the car? In the case of my own car the answer is easy...dirt has encased the dust and holds it there simply to remind me that the annual brush up is due!
Any scientists out there who could explain this phenomenon?
Not certain about this, but 2 reasons (although not sure if they'd be strong enough for this) that I can think of.
Electrostatic charge of the dust (clay etc) particles.
Also below a certain grain size you actually need more energy to get it into suspension (in the air/ water) than you do for some larger ones (although after a certain point it increases again). Once it's been lifted then it needs less energy, but the initial force needs to be greater.
Electrostatic charge of the dust (clay etc) particles.
Also below a certain grain size you actually need more energy to get it into suspension (in the air/ water) than you do for some larger ones (although after a certain point it increases again). Once it's been lifted then it needs less energy, but the initial force needs to be greater.
If you look at the speed of the air moving around your car, you will find that at the surface it is nearly stationary and the speed increases towards your airspeed as you move away from the surface over a distance of mm. This is the fluid boundary layer, and the dust grains are small enough to remain in this area.
The dust will most likely have been deposited by water, whose evaporation may have left a small residue holding the grains in place.
The dust will most likely have been deposited by water, whose evaporation may have left a small residue holding the grains in place.
Caruso said:
If you look at the speed of the air moving around your car, you will find that at the surface it is nearly stationary and the speed increases towards your airspeed as you move away from the surface over a distance of mm. This is the fluid boundary layer, and the dust grains are small enough to remain in this area.
The dust will most likely have been deposited by water, whose evaporation may have left a small residue holding the grains in place.
Johnnie likes this The dust will most likely have been deposited by water, whose evaporation may have left a small residue holding the grains in place.
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