Mechanical equilibrium of the system in gravitational field

Click For Summary

Discussion Overview

The discussion revolves around the mechanical equilibrium of a system situated in a gravitational field, specifically within a tall adiabatically isolating vessel. Participants explore the implications of pressure and density variations within the system after a period of settling, questioning the conditions for mechanical equilibrium in the context of non-uniform pressure and density distributions.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant describes a system in a gravitational field that reaches a uniform temperature but not uniform pressure or density, questioning if it is in mechanical equilibrium.
  • Another participant asserts that the system is in mechanical equilibrium without further elaboration.
  • A different participant expresses concern regarding the non-uniformity of pressure, suggesting that intensive parameters should be uniform in equilibrium.
  • In response, another participant argues that equilibrium can exist even with spatial variations in intensive parameters, as long as those parameters do not change over time.

Areas of Agreement / Disagreement

Participants express differing views on the definition of mechanical equilibrium, particularly regarding the implications of non-uniform pressure. There is no consensus on whether the system can be considered in mechanical equilibrium given the spatial pressure variation.

Contextual Notes

The discussion highlights the dependence on definitions of equilibrium and the interpretation of intensive parameters, with unresolved questions about the implications of spatial non-uniformity in pressure.

misko
Messages
46
Reaction score
0
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.
 
Physics news on Phys.org
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.
 
  • Like
Likes   Reactions: misko

Similar threads

  • · Replies 135 ·
5
Replies
135
Views
9K
  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 24 ·
Replies
24
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 18 ·
Replies
18
Views
3K
  • · Replies 9 ·
Replies
9
Views
13K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 6 ·
Replies
6
Views
1K