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.
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.
→ conservation; → momentum.
Fr.: tenseur énergie-quantité de mouvement
A tensor (Tμν) 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.
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.
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.
moment of momentum
Fr.: moment cinétique
Same as → angular momentum.
Fr.: quantité de movement
In → Newtonian mechanics, the momentum p of a body with → mass m and → velocity v is the product of these two quantities: p = mv. Momentum usually means → linear momentum as opposed to → angular momentum.
From L. momentum "movement, moving power," from movere "to move," → move.
Jonbâk, from jonb present stem of jonbidan "to move" (Mid.Pers. jumbidan, jumb- "to move," Lori, Laki jem "motion," related to gâm "step, pace;" O.Pers. gam- "to come; to go," Av. gam- "to come; to go," jamaiti "goes," gāman- "step, pac;" Mod.Pers. âmadan "to come;" Skt. gamati "goes;" Gk. bainein "to go, walk, step," L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE root *gwem- "to go, come") + -âk noun suffix.
orbital angular momentum
jonbâk-e zâviyeyi-ye madâri
Fr.: moment cinétique orbital, ~ angulaire ~
1) Mechanics: The → angular momentum
associated with the motion of a particle about an origin, equal to the cross product
of the position vector (r) with the linear momentum (p = mv):
L = r x p. Although r and p are constantly changing
direction, L is a constant in the absence of any external force on the system.
Also known as orbital momentum.
rotational angular momentum
jonbâk-e zâviyeyi-ye carxeši
Fr.: moment angulaire rotationnel, moment cinétique ~
The → angular momentum of a body rotating about an axis. The rotational angular momentum of a solid homogeneous sphere of mass M and radius R rotating about an axis passing through its center with a period of T is given by: L = 4πMR2/5T.
→ rotational; → angular; → momentum.
specific angular momentum
jonbâk-e zâvie-yi-ye âbizé
Fr.: moment angulaire spécifique
→ Angular momentum per unit mass.
spin angular momentum
jonbâk-e zâviyeyi-ye espin
Fr.: moment angulaire de spin
An intrinsic quantum mechanical characteristic of a particle that has no classical counterpart but may loosely be likened to the classical → angular momentum of a particle arising from rotation about its own axis. The magnitude of spin angular momentum is given by the expression S = ħ √ s(s + 1), where s is the → spin quantum number. As an example, the spin of an electron is s = 1/2; this means that its spin angular momentum is (ħ /2) √ 3 or 0.91 x 10-34 J.s. In addition, the projection of an angular momentum onto some defined axis is also quantized, with a z-component Sz = msħ. The only values of ms (magnetic quantum number) are ± 1/2. See also → Stern-Gerlach experiment.
Fr.: moment angulaire de vent
The product of the → mass loss rate and → terminal velocity used in the → radiation-driven wind theory. See also → modified wind momentum.