angular momentum jonbâk-e zâviye-yi Fr.: moment angulaire, moment cinétique The product of → moment of inertia and → angular velocity; synonymous with moment of momentum about an axis. Angular momentum is a vector quantity; it is conserved in an isolated system. |
angular momentum catastrophe negunzâr-e jonbâk-e zâviye-yi Fr.: catastrophe du moment angulaire A problem encountered by the → cold dark matter model of galaxy formation. The model predicts too small systems lacking → angular momentum, in contrast to real, observed galaxies. → cusp problem; → missing dwarfs. → angular; → momentum; → catastrophe |
angular momentum parameter pârâmun-e jonbâk-e zâviye-yi Fr.: paramètre de moment angulaire The ratio J/M, where J is the → angular momentum of a → rotating black hole and M the mass of the black hole. |
angular momentum problem parâse-ye jonbâk-e zâviye-yi Fr.: problème de moment angulaire 1) The fact that the Sun, which contains 99.9% of the mass of the
→ solar system, accounts for about 2% of the total
→ angular momentum of the solar system. The problem of outward
→ angular momentum transfer has been a main topic of interest for
models attempting to explain the origin of the solar system. |
angular momentum transfer tarâvaž-e jonbâk-e zâviye-yi Fr.: transfert de moment angulaire A process whereby in a rotating, non-solid system matter is displaced toward (→ accretion) or away from (→ mass loss) the rotation center. See also → magnetorotational instability. |
angular momentum transport tarâbord-e jonbâk-e zâviye-yi Fr.: transfert de moment angulaire Same as → angular momentum transfer. |
canonical momentum jonbâk-e hanjârvâr Fr.: moment cinétique canonique Same as → conjugate momentum. |
conjugate momentum jonbâk hamyuq Fr.: moment conjugué If q_{j} (j = 1, 2, ...) are generalized coordinates of a classical dynamical system, and L is its Lagrangian, the momentum conjugate to q_{j} is p_{j} = ∂L/∂q. Also known as canonical momentum. |
conservation of momentum pâyeš-e jonbâk Fr.: conservation de quantité de mouvement A fundamental law of physics which states that the momentum of a → physical system does not change in the course of time if there are no external forces acting on the system. It is embodied in → Newton's first law. This principle shows that the interaction of bodies composing a → closed system leads only to an exchange in momentum between the bodies but does not affect the motion of the system as a whole. More specifically, interactions between the composing bodies do not change the velocity of the system's → center of mass. → conservation; → momentum. |
dipole moment gaštâvar-e doqotbé (#) Fr.: moment dipolaire 1) The product of the strength of either of the charges in an
→ electric dipole and the distance separating the two charges.
It is expressed in → coulomb meters. Dipole moment is a
→ vector quantity.
Its direction is defined as toward the positive charge. In chemistry dipole moment is
a quantitative measure of polarity in a molecule;
the unit is the → debye. |
energy-momentum tensor tânsor-e kâruž-jonbâk Fr.: tenseur énergie-quantité de mouvement A tensor (T_{μν}) related to the → Einstein tensor through → Einstein's field equations. The energy-momentum tensor depends upon the distribution of the → energy and → matter in the space. |
generalized momenta jonbâkhâ-ye harvinidé Fr.: quantité de mouvement généralisée In → Lagrangian dynamics, momenta related to → generalized coordinates. For any system with n generalized coordinates q_{i} (i = 1, ..., n), generalized momenta are expressed by p_{i} = ∂L/∂q^{.}_{i}, where L is the → Lagrangian function. → generalized; → momentum. |
impulse-momentum principle parvaz-e tekâné-jonbâk Fr.: principe impulsion-quantité de mouvement The vector → impulse of the → resultant force on a particle, in any time interval, is equal in magnitude and duration to the vector change in momentum of the particle: ∫F dt = mv_{2} - mv_{1}. The impulse-momentum principle finds its chief application in connection with forces of short duration, such as those arising in collisions or explosions. Such forces are called → impulsive forces. |
linear momentum jonbâak-e xatti Fr.: quantité de mouvement linéaire The product of an object's → mass and → velocity. It is a → vector and points in the same direction as the velocity vector. Linear momentum is distinguished from → angular momentum. When there is no opportunity for confusion, usually the term momentum is used instead of linear momentum. |
magnetic dipole moment gaštâvar-e doqotbe-ye meqnâtisi Fr.: moment dipolaire magnétique Same as → magnetic moment. |
magnetic moment gaštâvar-e meqnâtisi (#) Fr.: moment magnétique 1) A measure of the strength of a magnet or current-carrying coil. In the case of
a bar magnet it is obtained by multiplying the distance between the two
magnetic poles by the average strength of the poles. Same as
→ magnetic dipole moment
See also → dipole moment. |
modified wind momentum jonbâk-e bâd-e vâtarzidé Fr.: moment angulaire de vent modifié A quantity defined as Π = (dM/dt) v_{∞} R^{0.5} for a star with radius R having a wind with → terminal velocity v_{∞} and a → mass loss rate dM/dt. There is a tight linear relation between the modified wind momenta and the stellar luminosities for → Population I→ O stars. See also → wind momentum. |
moment 1, 2) gaštâvar (#); 3) dam (#) Fr.: moment 1) Physics: An expression involving the → product
a → quantity, such as → force
or → mass, and its perpendicular → distance
from a reference point, such as → moment of force
(or → torque), → moment of inertia,
→ moment of momentum. From O.Fr. moment, from L. momentum "movement, moving power," also "instant, importance," contraction of *movimentum, from movere, → move. Gaštâvar literally "that which makes turn, turning agent," from
gašt "turning," past stem of
gaštan, gardidan "to turn,
to change" (Mid.Pers. vartitan; Av. varət- "to turn, revolve;"
Skt. vrt- "to turn, roll," vartate "it turns round, rolls;"
L. vertere "to turn;" O.H.G. werden "to become;"
PIE base *wer- "to turn, bend") + âvar
agent noun of
âvardan "to bring; to cause, produce"
(Mid.Pers. âwurtan, âvaritan; Av. ābar- "to bring; to possess,"
from prefix ā- + Av./O.Pers. bar- "to bear, carry,"
bareθre "to bear (infinitive)," bareθri
"a female that bears (children), a mother;" Mod.Pers. bordan "to carry;"
Skt. bharati "he carries;" Gk. pherein; L. fero "to carry"). |
moment of force gaštâvar (#) Fr.: moment, couple A measure of a force's tendency to cause a body to → rotate about a specified → axis. It is given by the force times the perpendicular → distance of the → line of action from the axis. Same as → torque |
moment of inertia gaštâvar-e laxti (#) Fr.: moment d'inertie A quantity which is a measure of the inertness of a body in rotatory motion about an axis. It is equal to the sum of the products of the masses of all particles of the body by the squares of their distances from this axis: I = Σm_{i}r_{i}^{2}, where r_{i} is the distance of the particle of mass m_{i} from the axis. Moment of inertia depends only upon the shape of the body and the arrangement of its mass with respect to the axis. For a solid sphere it is (2/5)MR^{2}. Moment of inertia is used in place of mass in problems involving rotation. Thus, the → angular momentum is Iω and → angular kinetic energy is (1/2)Iω^{2}, where ω is → angular velocity. |