> I thought that if you had something on a cushion of air you essentially have no friction.
They give a non-zero viscosity for the air/gas, so the friction won't be zero (although you're right it's probably very very low).
In a fluid film bearing, the relative movement of two surfaces with a viscous fluid (oil) between them creates friction in the process.
That's a similar situation to the moving air cushion, except the air/gas plays the role of the oil (*)
(*) in reality the dynamics of an air cushion are more complicated than a simple plain sliding bearing ... it's more like a rotating bearing with injected lift oil because of the air injected under pressure into the clearance which complicates the velocity profile in the clearance. But from the given information it seems pretty clear they intend to use a very simple model where the horizontal gas velocity Vx varies linearly across the depth of the air film in the y direction but is otherwise uniform across the 1m^2 area (no velocity variation in the z and x directions). The fluid shear dVx/dy of the viscous fluid creates friction.
> The weight will fall out of the viscosity and the fact that it's mushed down to 1mm thick.
Yes, the weight will not be part of the problem if that other info is specified. I don't think you can compute a weight from the limited info provided and the simple model suggested by the question.
> The question is a steady-state question so for this question there is friction which is somehow gotten from the area, weight, and desired speed.
Yes, fluid friction will be computed from film thickness, viscosity, area and speed. Weight not required if the other stuff is known.
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(2B)+(2B)' ?
