Sound waves versus equilibrium

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Discussion Overview

The discussion revolves around the concept of equilibrium in the context of a parcel of air transmitting sound waves. Participants explore definitions of equilibrium, particularly in relation to kinetic gas theory and thermodynamic principles, while questioning whether such a parcel can be considered in equilibrium.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant asserts that a parcel of air transmitting sound waves cannot be in a state of equilibrium.
  • Another participant requests clarification on the definition of equilibrium and its application to the situation.
  • A participant references kinetic gas theory, suggesting that a gas is in equilibrium when its entropy is maximized, arguing that sound waves indicate the gas is not at maximum entropy.
  • Another participant challenges the initial claim by stating that a system is in equilibrium when it has no tendency to change its properties, questioning whether the gas is an isolated system.
  • One participant notes that kinetic gas theory relies on assumptions that may not hold true, particularly regarding the elasticity of collisions.
  • A participant argues that a volume of air with sound waves does not meet the criteria for equilibrium as it is not an isolated system.
  • Several posts shift the discussion to the social dynamics of initiating conversations in forums, with participants reflecting on the timing of responses.

Areas of Agreement / Disagreement

Participants express differing views on the definition of equilibrium and its applicability to a parcel of air transmitting sound waves. There is no consensus on whether such a parcel can be considered in equilibrium.

Contextual Notes

Participants highlight the importance of definitions and assumptions in discussing equilibrium, particularly regarding isolated systems and the conditions under which entropy is maximized.

Who May Find This Useful

Individuals interested in thermodynamics, kinetic gas theory, and the conceptual nuances of equilibrium in physical systems may find this discussion relevant.

klimatos
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Postulate a parcel of air that is transmitting sound waves. Can that parcel ever be considered to be in a state of equilibrium? I maintain that it cannot. How say you?
 
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What is your definition of equilibrium?

Match this against the situation and post your answer.
 
Studiot said:
What is your definition of equilibrium?

Match this against the situation and post your answer.

Fair enough. Kinetic gas theory says a gas is in a state of equilibrium when its entropy has been maximized. I maintain that a gas transmitting sound waves is not in a state of maximum entropy. Consequently, the Ideal Gas Equation of State at Equilibrium would not apply to that parcel of air.
 
Kinetic gas theory says a gas is in a state of equilibrium when its entropy has been maximized.

Not quite.

A system is said to be in equilibrium when it has no further tendency to change its properties of interest.

In particular considering thermodynamic equilibrium (it is not the kinetic theory by the way) a system is isolated if the internal energy and volume are constant.

It can be shown that in an isolated system (with constant U and V) the entropy tends to a maximum.

So yes for an isolated system in equilibrium, the entropy is a maximum

Is your gas an isolated system?
 
Kinetic Gas Theory makes a whole range of assumptions which are not completely true. Complete elasticity of collisions is ALMOST completely true, but not quite.
 
We would not expect a volume of air with sound waves passing through it to satisfy the OPs definition of being in equilibrium because the volume of air is not an isolated system.
Why would anyone think it might be?

It is not clear what the point of the 1st post is.
If the intention is to start a conversation, as in social media, then isn't it more polite to kick things off yourself?
 
Simon Bridge said:
If the intention is to start a conversation, as in social media, then isn't it more polite to kick things off yourself?

I agree. Point taken. But why wait more than two years to bring this to my attention?
 
klimatos said:
I agree. Point taken. But why wait more than two years to bring this to my attention?
Because I'm an idiot?

I only just noticed and didn't check the date stamp - it happens :)
 
Simon Bridge said:
Because I'm an idiot?

I only just noticed and didn't check the date stamp - it happens :)

No harm, no foul.
 
  • #10
Red Wizard needs coffee - urgently!
 

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