Fr.: équilibre dynamique
Mechanics: The condition of a moving mechanical system when the accelerating force is balanced by an imaginary kinetic reaction according to → d'Alembert's principle. See also → static equilibrium; → thermodynamic equilibrium.
Fr.: équilibre dynamique
Of a physical system, a condition in which the parts of the system are in continuous motion, but they move in opposing directions at equal rates so that the system as a whole remains in equilibrium.
From L. æquilibrium, from æquus, → equal + libra "a balance, scale."
Tarâzmandi, noun of tarâzmand "in equilibrium," from tarâz "level; a level" + possession suffix -mand. The first component from tarâzu "balance, scales," Mid.Pers. tarâzên-, taraênidan "to weigh;" Proto-Iranian *tarāz-, from *tarā- "balance, scale" (cf. Skt. tulā- "scales, balance, weight," from tul- "to weigh, make equal in weight, equal," tolayati "weighs, balances;" L. tollere "to raise;" Gk. talanton "balance, weight," Atlas "the Bearer" of Heaven;" Lith. tiltas "bridge;" PIE base telə- "to lift, weigh") + Av. az- "to convey, conduct, drive," azaiti drives" (cf. Skt. aj- "to dive, sling," ájati "drives," ajirá- "agile, quick;" Gk. agein "to lead, guide, drive, carry off;" L. agere "to do, set in motion, drive," from PIE root *ag- "to drive, move," → act).
naheš-e tarâzmandi (#)
Fr.: position d'équilibre
The position of an oscillating body at which no net force acts on it.
estât-e tarâzmandi, hâlat-e ~
Fr.: état d'équilibre
tarâzmandi-ye gerâneši (#)
Fr.: équilibre gravitationnel
The condition in a celestial body when gravitational forces acting on each point are balanced by some outward pressure, such as radiation pressure or electron degeneracy pressure, so that no vertical motion results.
Fr.: équilibre hydrodynamique
The state of a star when all its internal forces are in equilibrium. The main forces are gas pressure, radiation pressure due to thermonuclear fusion that tends to disrupt the star, and the opposing gravity. → hydrostatic equilibrium.
Fr.: équilibre hydrostatique
1) The physical situation reached in a fluid when complete balance exists between
the internal pressure at any point and the weight of the material above the point.
local thermodynamic equilibrium (LTE)
tarâzmandi-ye garmâtavânik-e mahali
Fr.: équilibre thermodynamique local
The assumption that all distribution functions characterizing the material and its interaction with the radiation field at a point in the star are given by → thermodynamic equilibrium relations at local values of the temperature and density.
Fr.: équilibre mécanique
1) The state of a → rigid body if, as viewed from an
→ inertial frame of rest: 1) the
→ linear acceleration of its
→ center of mass is zero, and 2) its
→ angular acceleration about any axis
fixed in this reference frame is zero. The center of mass may
be moving with constant velocity and the body may be rotating
about a fixed axis with constant angular velocity.
non-local thermodynamic equilibrium (NLTE)
tarâzmandi-ye garmâtavânik-e nâmahali
Fr.: hors équilibre thermodynamique local
A physical condition in which the assumption of the → local thermodynamic equilibrium does not hold.
nuclear statistical equilibrium (NSE)
tarâzmandi-ye âmâri-ye haste-yi
Fr.: équilibre statistique nucléaire
In → nucleosynthesis models, the condition in which all nuclear species are in equilibrium under exchange of → protons and → neutrons. Matter in nuclear statistical equilibrium is characterized by a large abundance of iron peak nuclei. In such equilibria abundance of each nuclide can be calculated from repeated application of → Saha equation.
Fr.: équilibre de phases
The condition of temperature and pressure under which different phases (e.g. gas, liquid, and solid) of a substance coexist.
Fr.: équilibre radiatif
The balance between radiative emission and radiative absorption in a specified system.
tarâzmandi-ye pâydâr (#)
Fr.: équilibre stable
An equilibrium state of a system in which if a small perturbation away from equilibrium is applied, the system will return to its equilibrium state. An example is a pendulum hanging straight down. If it is pushed slightly, it will experience a force back toward the equilibrium position. It may oscillate around the equilibrium position for a while, but it will finally regain its equilibrium position. → unstable equilibrium.
Fr.: équilibre statique
The state of a rigid body which is not moving at all. The conditions for static equilibrium are: 1) the sum of the external forces on the object must equal zero, and 2) the sum of the → torques must equal zero. See also → dynamic equilibrium and → mechanical equilibrium.
Fr.: équilibre statistique
A state in which the average density of atoms per cubic centimeter in any atomic state does not change with time and in which, statistically, energy is equally divided among all degrees of freedom if classical concepts prevail.
tarâzmandi-ye garmâyi (#)
Fr.: équilibre thermique
In thermodynamics, the state of a system all parts of which have attained a uniform temperature and no net heat exchange is taking place between it and its surroundings. If two bodies are in thermal equilibrium, they have the same temperature. Thermal equilibrium is the central criterion of the → zeroth law of thermodynamics. See also → local thermodynamic equilibrium (LTE).
Fr.: équilibre thermodynamique
The condition of a → thermodynamic system in which the available → energy is distributed uniformly among all the possible forms of energy. Furthermore, all → thermodynamic process es must be exactly balanced by their reverse processes. For example, inside a star there will be as many → ionizations of helium per second as there are → recombinations of free electrons and helium ions. Se also → local thermodynamic equilibrium (LTE).
Fr.: équilibre instable
An equilibrium state of a system in which if a small perturbation away from equilibrium is applied, the system will move farther away from equilibrium state. For example, mechanical equilibrium in which the potential energy is a maximum, as a sphere placed on top of a hill. Mathematically, if the second derivative of the energy with respect to the coordinate of interest is negative, the system is in an unstable equilibrium. → stable equilibrium.