[ad. L. accelerātiōn-em, n. of action f. accelerā-re: see ACCELERATE a. and -ION. Cf. mod. Fr. accélération.]
1. The action or process of accelerating, quickening or hastening.
1531. Elyot, Governour (1834), 117. Who beholding … the acceleration or haste to his [Cæsar’s] confusion, caused by his own edict or decree, will not commend affability.
1663. Cowley, Verses & Essays (1669), 45. A Garden, destined to the tryal of all manner of Experiments concerning Plants, as their Melioration, Acceleration, Retardation, Conservation.
1732. Arbuthnot, Rules of Diet, 266. Those things which take off the Causes of Acceleration retard the Motion of the Blood.
1822. Imison, Sci. & Art, I. 84. But the friction of the teeth and the resistance of the air check this acceleration.
2. The condition of being accelerated or hastened; increased speed.
1534. Ld. Berners, G. Boke of M. Aurel. (1546), F. viij. b. Gret acceleracion in busynesses nowe presente maketh greate inconueniences in tyme to come.
1784. Johnson, in Boswell (1816), IV. 455. No, sir; you cannot conceive with what acceleration I advance towards death.
3. The extent to which anything is accelerated; in Nat. Phil. the rate of increase of velocity per unit of time. Uniform or constant acceleration: the unvarying amount per second added to the velocity or rate at which a body is moving, e.g., under the influence of gravity.
1656. trans. Hobbes’s Elem. of Philos. (1839), 232. The body will be carried through the same strait line … provided it have like acceleration.
1677. Hale, Prim. Orig. Man., 5. There be many things touching Matters Physical … as concerning the degrees of acceleration of Motion.
1794. G. Adams, Nat. & Exper. Phil., III. xxvii. 118. The law of acceleration, in falling bodies, was not discovered till the time of Galileo.
1876. Tait, Rec. Adv. in Phys. Sc., xiv. 352. Rate of change of velocity is called in kinematics, acceleration.
1879. Thomson & Tait, Nat. Phil., I. I. § 28. The velocity of a point is said to be accelerated or retarded according as it increases or diminishes, but the word acceleration is generally used in either sense, on the understanding that we may regard its quantity as either positive or negative.
4. Astr. and Physics. Acceleration of the fixed stars; the time (3′ 55.9″) which the stars gain upon the sun in passing the meridian each day, or by which the sidereal day is shorter than the solar, due to the advance of the earth in her orbit while revolving on her axis. Of the planets, the increased velocity with which they advance from aphelion to perihelion. Of the moon, an increase (of about 11″ in the century) in the rapidity of the moon’s mean motion, discovered by Halley. Of the tides, the amount by which from special causes, high or low water occurs at any place before the calculated time.
1849. Mrs. Somerville, Connex. of Phys. Sc., § 5. 43. This secular increase in the moon’s velocity is called the Acceleration.
