What is Equilibrium: Definition and 1000 Discussions

Thermodynamic equilibrium is an axiomatic concept of thermodynamics. It is an internal state of a single thermodynamic system, or a relation between several thermodynamic systems connected by more or less permeable or impermeable walls. In thermodynamic equilibrium there are no net macroscopic flows of matter or of energy, either within a system or between systems.
In a system that is in its own state of internal thermodynamic equilibrium, no macroscopic change occurs.
Systems in mutual thermodynamic equilibrium are simultaneously in mutual thermal, mechanical, chemical, and radiative equilibria. Systems can be in one kind of mutual equilibrium, though not in others. In thermodynamic equilibrium, all kinds of equilibrium hold at once and indefinitely, until disturbed by a thermodynamic operation. In a macroscopic equilibrium, perfectly or almost perfectly balanced microscopic exchanges occur; this is the physical explanation of the notion of macroscopic equilibrium.
A thermodynamic system in a state of internal thermodynamic equilibrium has a spatially uniform temperature. Its intensive properties, other than temperature, may be driven to spatial inhomogeneity by an unchanging long-range force field imposed on it by its surroundings.
In systems that are at a state of non-equilibrium there are, by contrast, net flows of matter or energy. If such changes can be triggered to occur in a system in which they are not already occurring, the system is said to be in a meta-stable equilibrium.
Though not a widely named "law," it is an axiom of thermodynamics that there exist states of thermodynamic equilibrium. The second law of thermodynamics states that when a body of material starts from an equilibrium state, in which, portions of it are held at different states by more or less permeable or impermeable partitions, and a thermodynamic operation removes or makes the partitions more permeable and it is isolated, then it spontaneously reaches its own, new state of internal thermodynamic equilibrium, and this is accompanied by an increase in the sum of the entropies of the portions.

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  1. S

    Thermal Equilibrium and Longitudinal Relaxation

    Homework Statement Problem 6.2 from Magnetic Resonance Imaging: Physical Principles and Sequence Design. Show that M_o \approx \rho_o \frac{s(s+1)\gamma^2\hbar^2}{3kT}B_o Homework Equations M_o = \rho_o \gamma \hbar \frac{\sum m_s e^{m_s(\hbar w_o / kT)}}{\sum e^{m_s(\hbar w_o / kT)}} ...
  2. R

    Determine maximum weight and angle for equilibrium

    Homework Statement The cords ABC and BD can each support a maximum load of 100 lb. Determine the weight of the crate, and the angle θ for equilibrium. Homework Equations ∑F= 0 ∑Fx=0 ΣFy=0 Setting derivative of an expression to zero To find critical point Second derivative test for determining...
  3. Z

    Vector multiplication in static equilibrium

    Homework Statement A 1 200-N uniform boom at 65 degrees to the vertical is supported by a cable at an angle of 25 degrees to the horizontal . The boom is pivoted at the bottom, and an object of weight = 2 000 N hangs from its top. Find the tension in the support cable Homework EquationsThe...
  4. M

    Pressure and Equilibrium of Decomposition

    Homework Statement SO3 decomposes on heating: 2SO2(g) 2SO2(g) + O2(g) A sample of pure SO3 was heated to a high temperature T. At equilibrium, the mole ratio of SO2 to SO3 was 0.152 and the total pressure was 2.73 atm. If the piston was pushed into cut the volume in half what is the new...
  5. gracy

    Unstable equilibrium in case of dipoles

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  6. Z

    Static equilibrium involving toque

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  7. Titan97

    Buffer Action and Titration: Does the Process Ever End?

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  8. Titan97

    Titration of amino acid with strong base

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  9. Titan97

    Hydrolysis of salt containing amphiprotic anion

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  10. Handsome jack

    How Can You Find Forces P, F, and T in a Static Equilibrium Problem?

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  11. V

    Equilibrium of forces lab- Sources of error spring scale

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  12. H

    How to find forces in wires at equilibrium

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  13. Titan97

    Question on chemical equilibrium

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  14. Titan97

    Effect on equilibrium, addition of inert gas

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  15. A

    Equilibrium of a spring and speed.

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  16. I

    Can IESDS Determine the Nash Equilibrium in a Game?

    Hello everyone! Applying the Iterated Elimination of Strictly Dominated Strategies (IESDS) to a game resulted with the solution of the Nash Equilibrium. Actually that specific "quadrant" of the matrix is the: * Pareto optimal * Nash Equilibrium * Dominant strategies (through IESDS). This is...
  17. Sarah00

    Static Equilibrium: Net Force & Torque = 0

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  18. P

    Non equilibrium thermodynamics: T as a function of time

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  19. Dopplerganger

    Recognize this irreversible equation for kinetic modeling?

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  20. toforfiltum

    Proving tension in rope of equilibrium system

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  21. rpthomps

    What Is the Minimum Coefficient of Friction Needed for a Sphere Against a Wall?

    Homework Statement A uniform sphere of radius R is supported by a rope attached to a vertical wall,as shown in the figure. The point where the rope is attached to the sphere is located so a continuation of the tope would intersect a horizontal line through the sphere’s centre a distance R/2...
  22. Sarah00

    Static Equilibrium Homework: Net Force and Torque Solutions

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  23. J-dizzal

    Static equilibrium. Friction example

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  24. J-dizzal

    Static equilibrium, machines; handheld press

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  25. J-dizzal

    Static equilibrium problem -- with a pulley

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  26. J-dizzal

    Static equilibrium, trusses/section method

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  27. C

    Tension and Equilibrium: Hanging sign

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  28. J-dizzal

    Static equilibrium of a beam, 2 force and 3 force member?

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  29. J-dizzal

    Statics, equilibrium sphere in a groove on an incline plane

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  30. M

    What is dynamic equilibrium in laymen's terms?

    I was receiving help for the following problem... The 2.0 kg wood box in the figureslides down a vertical wood wall while you push on it at a 45 ∘ angle. The coefficient of kinetic friction of wood on wood is μk = 0.200. What magnitude of force should you apply to cause the box to slide down at...
  31. J-dizzal

    Static equilibrium 3D, traffic light problem

    Homework Statement The vertical and horizontal poles at the traffic-light assembly are erected first. Determine the additional force and moment reactions at the base O caused by the addition of the three 100-lb traffic signals B, C, and D. Report your answers as a force magnitude and a moment...
  32. J-dizzal

    Static equilibrium minimum cylinder mass problem

    Homework Statement Determine the minimum cylinder mass m1 required to cause loss of contact at A. Homework Equations ΣF=0, ΣM=0 The Attempt at a Solution Im not sure where to go with this one. the solution would be in terms of mass(m)
  33. Coffee_

    Assumption of thermal equilibrium for ensembles

    Take for example a canonical ensemble, to use the derived distributions and probabilities, the considered system has to be in thermal equilibrium with the heat bath. Where in the derivation of the probabilities and distributions do we usually assume this? There is a point that I can identify...
  34. J-dizzal

    Static equilibrium; pulley and inclined plane problem.

    Homework Statement What weight WB will cause the system to be in equilibrium? Neglect all friction, and state any other assumptions. Homework Equations ΣF=0 The Attempt at a Solution I can't figure out what I am doing wrong with these pully problems, I tried putting in resultant forces at...
  35. J-dizzal

    Static force equilibrium problem involving simply pully syst

    Homework Statement A former student of mechanics wishes to weigh himself but has access only to a scale A with capacity limited to 120 lbs and a small 20-lb spring dynamometer B. With the rig shown he discovers that when he exerts a pull on the rope so that B registers 19 lb, the scale A reads...
  36. K

    Kinetic equilibrum and chemical equilibrium

    All particle species are in equilibrium at early times of the universe. But I didn't find any book that makes the difference of kinetic and chemical equilibrium clear. I have some of my own opinions and I hope to get your comments: (1) kinetic equilibrium means the distribution function obeys...
  37. 0

    Ideal Gas Law Equilibrium Requirements

    It is well known that the ideal gas law applies only to an ideal gas, one consisting of particles infinitesimal in size and exhibits no interactions between the particles. Considering an ideal gas, is the ideal gas law valid under non-equilibrium conditions? For example, does the ideal gas law...
  38. UMath1

    Cantilever equilibrium problem

    I am trying to resolve for the forces in the attached diagram. In order for this object to be in rotational equilibrium, the torques of the normal force and the garvitational force would have to be equal. However, this would imply that normal force produced by the fulcrum would be far greater...
  39. A

    Thermal Equilibrium: How Objects Reach Balance

    Hello, What "path" do objects take to reach thermal equilibrium? Does heat from a hot part sitting in room temperature air like to travel through the most thermally conductive portions? My thought is that it is similar to current in a circuit taking the path of least resistance (where the most...
  40. K

    A marble that is rolling without slipping approaches a hill

    Homework Statement A marble that is rolling without slipping approaches a hill at 8.5 m/s. How high vertically will the marble go under these circumstances: If the hill is rough enough to prevent any slipping? If the hill is perfectly smooth? Why does the marble rise to different heights when...
  41. C

    Chemical potential equilibrium cosmology

    In Dodelson's "Introduction to Modern Cosmology" at p. 61 he introduces a non- equilibrium number density $$n_i = g_i e^{\mu_i/T} \int \frac{d^3p}{(2\pi)^3} e^{-E_i/T}$$ and an equilibrium number density $$n_i^{(0)} = g_i \int \frac{d^3p}{(2\pi)^3} e^{-E_i/T},$$ from which it follows that the...
  42. Sivaraman

    Homogeneous equilibrium model-fluid flow

    Hello,I am trying to calculate the velocity in a pipe with length L and Dia D, which is connected to bottom of a pressurized vessel (Vessel dimensions are known, Level of liquid inside the vessel is known). Now i need to figure out the velocity as a function of pressure inside the vessel.We can...
  43. M

    Equilibrium of Charges on a Square: Find q

    four charges each equal -Q placed at the four edges of a square and a charge q is placed at the centre. if system is in equilibrium the value of q is, the answer is q = Q/4 * ( 1 + 2(√2) can anyone please solve this, would be great
  44. M

    Rotational equilibrium equation - Moment of Forces (2D prob)

    Homework Statement The landing gear of an aircraft is composed of a main leg OA (with a weight including the wheel is 1000N to G) and two secondary links BC and 50cm long each CD. The DC link forms an angle θ of 30 degrees with the vertical. a) Add the rotational equilibrium equation with...
  45. GM Jackson

    How does a black body emit as much energy as it absorbs?

    Homework Statement A black body absorbs all incident electromagnetic radiation, including visible light which has wavelengths from 380nm to 750nm. IR radiation has wavelengths that are so long they are measured in microns. That suggests that visible light has a higher frequency than IR, and...
  46. Aravind Raj

    Physical meaning of equations of equilibrium

    From the equations of equilibrium "σy+(∂σy/∂y)*(lower case delta y)" is the force acting along y direction. can anybody explain the physical meaning of the second part of the force where we multiply delta and del?
  47. D

    How Does Adding Water Affect the Equilibrium in the BiOCl Dissolution Reaction?

    Hey everyone, At the moment I am stuck with an example and was wondering if someone could please explain it to me: You have the equation: BiOCl(s) + 2H+(aq) -><- Bi3+(aq) +Cl-(aq) +H2O(l) Why is it that when you add extra water to the system, there is no change to the equilibrium? I would...
  48. Curieuse

    How Much Force is Needed to Lift a Wheel Over an Obstacle?

    1. Problem statement In figure, what magnitude of (constant) force F applied horizontally at the axle of the wheel is necessary to raise the wheel over an obstacle of height h=3.00cm ? The wheel's radius is r=6.00cm , and it's mass is m=0.800 kg. Homework Equations Balance of forces: Fnet=0...
  49. goonking

    Solving for Equilibrium: Water vs Mercury

    Homework Statement Homework Equations P1= Patm + ρwatervg P2= Patm + ρmer.vg The Attempt at a Solution so both sides of the tubes are open to atmosphere pressure and are in equilibrium. I can get P1 =P2 the 1 atm from each side cancels out. g (gravity) cancels out I'm left with volume (or...
  50. K

    Are two charges always in electrostatic equilibrium?

    What I studied was that the force on one charge due to another equal charge in the system of two charges was, (say) F; whereas the force on the other charge due to the first charge was found out to be -F. Hence they add up to be zero. So can I say that the two equal charges are in electrostatic...
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