| 释义 |
momentum|məʊˈmɛntəm|
Pl. -ta.
[a. L. mōmentum: see moment n.]
†1. = moment 3 b. Obs.
1735B. Robins Disc. Newton's Meth. Fluxions 75 Sir Isaac Newton's definition of momenta, That they are the momentaneous increments or decrements of varying quantities, may possibly be thought obscure.
†2. ‘Impulsive weight’ (J., s.v. Moment); force of movement. Obs.
1740Cheyne Regimen 109 The Particles of Mercury have the greatest Momentum and Force. 1754–64Smellie Midwif. I. 107 In young people the Momentum of the circulating fluid is greater than the resisting force of the Solids. 1817Coleridge ‘Blessed are ye’ 84 The short interruptions may be well represented as a few steps backward, that it might leap forward with an additional momentum.
†3. Mech. = moment n. 8 b. Obs.
1839Penny Cycl. XV. 311 Momentum, or Moment, of Inertia.
4. a. Mech. The ‘quantity of motion’ of a moving body; the product of the mass by the velocity of a body. angular momentum (see quot. 1870).
1699J. Keill Exam. Refl. Th. Earth 10 According to the Laws of motion, the momentum or quantity of motion of both bodies taken together would remain the same. 1727–41Chambers Cycl. s.v. Moment, In comparing the motions of bodies, the ratio of their momenta is always compounded of the quantity of matter, and the celerity of the moving body. 1870Everett Deschanel's Nat. Philos. 75 The angular momentum of a rotating body is a name given to the product of the moment of inertia and the angular velocity. 1882Minchin Unipl. Kinemat. 106 The momentum of a moving particle in any direction is defined to be the product of the number of units of mass in the particle and the number of units of velocity in its component of velocity in that direction.
b. Hence, in popular use, applied to the effect of inertia in the continuance of motion after the impulse has ceased; impetus gained by movement.
1860Tyndall Glac. i. xxvii. 216 His momentum rolled him over and over down the incline. 1874H. R. Reynolds John Bapt. iii. iii. 189 Every drop of the Nile or the Ganges has been..lifted by the sunbeam to the height, the fall from which give the momentum of its onward passage to the sea.
Comb.1880C. & F. Darwin Movem. Pl. 508 This momentum-like movement probably results from the accumulated effects of apogeotropism.
c. fig.
1782V. Knox Ess. I. lviii. 257 Such genius..makes itself felt by its own native force, and bears all before it by an irresistible momentum. 1790Burke Fr. Rev. Wks. V. 100 That momentum of ignorance,..presumption, and lust of plunder, which nothing has been able to resist. 1868Kinglake Crimea (1877) III. i. §44. 308 Ambition lends strength and momentum to the purposes of a general. 1902A. B. Davidson Bibl. & Lit. Ess. vii. 188 Faustus Socinus gave a new momentum to the exposition of the Epistle.
5. = moment n. 9.
1829Sir W. Hamilton Discuss. (1852) 31 You have all the momenta whose relation and notion constitute the reality of knowledge. 1874Morris tr. Ueberweg's Hist. Philos. II. 232 The momenta of Quantity are: pure quantity, quantum, and degree. 1903A. B. Davidson O.T. Prophecy viii. 114 Revelation..was in all cases part of the life of the individual, a momentum in the spiritual relations of him and God.
6. Special Comb.: momentum space Physics, a three-dimensional space in which each particle of a physical system is represented by a point whose three Cartesian co-ordinates are numerically equal to the components of its momentum in the directions of the three co-ordinate axes.
1948W. Hume-Rothery Electrons, Atoms, Metals & Alloys xx. 143 The momentum space is divided into little cells of side h/L, and volume h3/L3. 1970I. E. McCarthy Nuclear Reactions i. v. 111 We consider the matrix element in momentum space. 1970G. K. Woodgate Elem. Atomic Struct. vi. 98 Under this assumption the electrons are moving freely, with no forces acting on them, and their translational momenta can be taken to be directed isotropically in momentum space. |