equilibrium

Examples of equilibrium in the following topics:

• First Condition

  • The first condition of equilibrium is that the net force in all directions must be zero.
  • For an object to be in equilibrium, it must be experiencing no acceleration.
  • The condition $F_\text{net} = 0$ must be true for both static equilibrium, where the object's velocity is zero, and dynamic equilibrium, where the object is moving at a constant velocity.
  • Below, the motionless person is in static equilibrium.
  • This car is in dynamic equilibrium because it is moving at constant velocity.

• The Zeroth Law of Thermodynamics

  • The Zeroth Law of Thermodynamics states that systems in thermal equilibrium are at the same temperature.
  • If A and C are in thermal equilibrium, and A and B are in thermal equilibrium, then B and C are in thermal equilibrium.
  • Temperature is the quantity that is always the same for all systems in thermal equilibrium with one another.
  • The double arrow represents thermal equilibrium between systems.
  • If systems A and C are in equilibrium, and systems A and B are in equilibrium, then systems B and C are in equilibrium.

• Translational Equilibrium

  • This implies two types of possible equilibrium.
  • Static or dynamic, these kinds of equilibrium can be categorized as translational equilibrium.
  • Examples of translational equilibrium are all around us.
  • These six forces are in equilibrium.
  • Assess the role each type of equilibrium plays in mechanical devices

• A Review of the Zeroth Law

  • Zeroth law justifies the use of thermodynamic temperature, defined as the shared temperature of three designated systems at equilibrium.
  • The Zeroth Law of Thermodynamics states: If two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system, C, then A is also in thermal equilibrium with C.
  • Two systems are in thermal equilibrium if they could transfer heat between each other, but don't.
  • Indeed, experiments have shown that if two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system C, then A is also in thermal equilibrium with C.
  • The objects are then in thermal equilibrium, and no further changes will occur.

• Second Condition

  • The second condition of static equilibrium says that the net torque acting on the object must be zero.
  • A child's seesaw, shown in , is an example of static equilibrium.
  • An object in static equilibrium is one that has no acceleration in any direction.
  • If a given object is in static equilibrium, both the net force and the net torque on the object must be zero.
  • The system is in static equilibrium, showing no acceleration in any direction.

• Stability, Balance, and Center of Mass

  • An object in static equilibrium remains in the same state forever, but not all forms of equilibrium are the same.
  • To quantify equilibrium for a single object, there are two conditions:
  • Our notion of "balance" comes directly from the formulation of equilibrium.
  • It might have been initially "balanced" and at equilibrium, but it was an unstable equilibrium, prone to being disturbed.
  • This is an example of unstable equilibrium.

• LTE

  • To derive these relations we have not made any assumptions about whether the photons or the matter are in thermal equilibrium with themselves or each other.
  • An extremely useful assumption is that the matter is in thermal equilibrium at least locally (Local Thermodynamic Equilibrium).
  • In this case the ratio of the number of atoms in the various states is determined by the condition of thermodynamic equilibrium
  • Because the source function equals the blackbody function, does this mean that sources in local thermodynamic equilibrium emit blackbody radiation?

• The Evaporating Atmosphere

  • At equilibrium, evaporation and condensation processes exactly balance and there is no net change in the volume of either phase.
  • At equilibrium, evaporation and condensation processes exactly balance and there is no net change in the volume of either phase.
  • At room temperature and pressure, the water jar reaches equilibrium when the air over the water has a humidity of about 3%.
  • At 100 °C and atmospheric pressure, equilibrium is not reached until the air is 100% water.
  • It is in a phase equilibrium.

• Static Equilibrium

  • Static equilibrium is a particular state of a physical system.
  • As it pertains to fluidics, static equilibrium concerns the forces acting on a static object within a fluid medium.
  • For a fluid at rest, the conditions for static equilibrium must be met at any point within the fluid medium.
  • For static equilibrium to be achieved, the sum of these forces must be zero, as shown in .
  • This figure shows the equations for static equilibrium of a region within a fluid.

• Conductors and Fields in Static Equilibrium

  • In the presence of charge or an electric field, the charges in a conductor will redistribute until they reach static equilibrium.
  • Once the charges are redistributed, the conductor is in a state of electrostatic equilibrium.
  • It should be noted that the distribution of charges depends on the shape of the conductor and that static equilibrium may not necessarily involve an even distribution of charges, which tend to aggregate in higher concentrations around sharp points.
  • Describe behavior of charges in a conductor in the presence of charge or an electric field and under static equilibrium