Mechanical equilibrium of the system in gravitational field

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A system in a tall adiabatically isolating vessel under a steady gravitational field will eventually reach a uniform temperature but exhibit varying pressure and density due to gravity. Despite the spatial variation in pressure, the system can still be considered in mechanical equilibrium because there are no macroscopic changes over time. The key distinction is that equilibrium refers to temporal stability rather than spatial uniformity of intensive parameters. Therefore, while pressure is not uniform throughout the vessel, the system remains in mechanical equilibrium. This highlights the difference between intensive parameters and the conditions for mechanical equilibrium.
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Consider a system contained in a very tall adiabatically isolating vessel with rigid walls initially containing a thermally heterogeneous distribution of material, left for a long time under the influence of a steady gravitational field, along its tall dimension, due to an outside body such as the earth. It will settle to a state of uniform temperature throughout, though not of uniform pressure or density.

Pressure and density will be higher in the lower part of the vessel due to gravity. Is this system in mechanical equilibrium? I mean, we don't have macroscopic change of the pressure in the system once everything is settled down, but pressure is not spatially uniform and it depends on the height we measure it.
 
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misko said:
Is this system in mechanical equilibrium?

Yes.
 
Ok but what bothers me is that pressure is not spatially uniform. Since pressure is intensive parameter, shouldn't the system in equilibrium have intensive parameters same in all points?
 
misko said:
Since pressure is intensive parameter, shouldn't the system in equilibrium have intensive parameters same in all points?
No. Equilibrium means that the parameter doesn't change with respect to time. It can still change with respect to space.
 
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