Fr.: moment angulaire, moment cinétique
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 parameter
pârâmun-e jonbâk-e zâviye-yi
Fr.: paramètre de moment angulaire
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
angular momentum transport
tarâbord-e jonbâk-e zâviye-yi
Fr.: transfert de moment angulaire
Same as → angular momentum transfer.
Fr.: moment cinétique canonique
Same as → conjugate momentum.
Fr.: moment conjugué
If qj (j = 1, 2, ...) are generalized coordinates of a classical dynamical system, and L is its Lagrangian, the momentum conjugate to qj is pj = ∂L/∂q. Also known as canonical momentum.
conservation of momentum
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.
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.
Fr.: tenseur énergie-quantité de mouvement
Fr.: quantité de mouvement généralisée
In → Lagrangian dynamics, momenta related to → generalized coordinates. For any system with n generalized coordinates qi (i = 1, ..., n), generalized momenta are expressed by pi = ∂L/∂q.i, where L is the → Lagrangian function.
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 = mv2 - mv1. 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.
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.
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∞ R0.5 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.
1, 2) gaštâvar (#); 3) dam (#)
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
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 = Σmiri2, where ri is the distance of the particle of mass mi 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)MR2. 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)Iω2, where ω is → angular velocity.