| 释义 |
free fall
free fall or free·fall (frē′fôl′)n.1. The fall of a body within the atmosphere without a drag-producing device such as a parachute.2. The ideal falling motion of a body that is subject only to the earth's gravitational field.3. Rapid uncontrolled decline: "The markets threatened to go into free fall and we came within an eyelash of ... an uncontrollable panic" (Felix Rohatyn).
free′fall′ v.free fall n 1. (General Physics) free descent of a body in which the gravitational force is the only force acting on it 2. (Aeronautics) the part of a parachute descent before the parachute opens free′ fall′
n. 1. the hypothetical fall of a body such that the only force acting upon it is gravity. 2. the part of a parachute jump that precedes the opening of the parachute. [1915–20] free-fall (v. ˈfriˌfɔl; n. -ˈfɔl)
v. -fell, -fall•en, -fall•ing,
n. v.i. 1. (of a parachutist) to descend in a free fall. n. 2. free fall. [1915–20] free fallA parachute maneuver in which the parachute is manually activated at the discretion of the jumper or automatically at a preset altitude. See also airdrop; air movement; free drop; high velocity drop; low velocity drop.Thesaurus| Noun | 1. |  free fall - the ideal falling motion of something subject only to a gravitational fielddrop, fall - a free and rapid descent by the force of gravity; "it was a miracle that he survived the drop from that height" | | 2. | free fall - a sudden sharp decrease in some quantity; "a drop of 57 points on the Dow Jones index"; "there was a drop in pressure in the pulmonary artery"; "a dip in prices"; "when that became known the price of their stock went into free fall"drop, dip, falldecrement, decrease - the amount by which something decreasescorrection - a drop in stock market activity or stock prices following a period of increases; "market runups are invariably followed by a correction"voltage drop - a decrease in voltage along a conductor through which current is flowing |
Translationsfree fall
free fall1. A vertical descent of a physical body in which gravity is the only force acting upon it. If they were in true free fall, a feather and a bowling ball would both fall to the ground at the same rate.2. In a parachute jump, the period of vertical descent leading up to and immediately before the parachute is opened. I get such a rush from the free fall when I skydive that I often wish I didn't have to open my chute at all!3. By extension of def. 1, any sudden, rapid, and uncontrollable decline (e.g., in value, reputation, success, etc.) that continues unabated for an indefinite length of time. The stock market went into a free fall after the housing market collapsed. After getting busted by the police for using marijuana last year, John's life has been in a free fall.See also: fall, freefree fallA rapid, uncontrolled decline, as in The markets threatened to go into free fall and we came close to outright panic. This term transfers the aeronautical meaning of a free fall, that is, "a fall through the air without any impedance, such as a parachute," to other kinds of precipitous drop. [Second half of 1900s] See also: fall, freefree fall
free fall, in physics, the state of a body moving solely under the influence of gravitational forces (see gravitationgravitation,
the attractive force existing between any two particles of matter. The Law of Universal Gravitation
Since the gravitational force is experienced by all matter in the universe, from the largest galaxies down to the smallest particles, it is often called
..... Click the link for more information. ). A body falling freely toward the surface of the earth undergoes an accelerationacceleration,
change in the velocity of a body with respect to time. Since velocity is a vector quantity, involving both magnitude and direction, acceleration is also a vector. In order to produce an acceleration, a force must be applied to the body.
..... Click the link for more information. due to gravity of 32 ft/sec2 (9.8 m/sec2), which is symbolized by g.Free fall The accelerated motion toward the center of the Earth of a body acted on by the Earth's gravitational attraction and by no other force. If a body falls freely from rest near the surface of the Earth, it gains a velocity of approximately 9.8 m/s every second. Thus, the acceleration of gravity g equals 9.8 m/s2 or 32.16 ft/s2. This acceleration is independent of the mass or nature of the falling body. For short distances of free fall, the value of g may be considered constant. After t seconds the velocity vt of a body failing from rest near the Earth is given by Eq. (1). (1)  If a falling body has an initial constant velocity in any direction, it retains that velocity if no other forces are present. If other forces are present, they may change the observed direction and rate of fall of the body, but they do not change the Earth's gravitational pull; therefore a body may still be thought of as freely “failing’’ even though the resultant observed motion is upward. For a body failing a very large distance from the Earth, the acceleration of gravity can no longer be considered constant. According to Newton's law of gravitation, the force between any two bodies varies inversely with the square of the distance between them; therefore with increasing distance between any body and the Earth, the acceleration of the body toward the Earth decreases rapidly. The final velocity vf, attained when a body falls freely from an infinite distance to the surface of the Earth, is given by Eq. (2), (2) where R is the radius of the Earth, which gives a numerical value of 11.3 km/s or 7 mi/s. This is consequently the “escape velocity,’’ the initial upward velocity for a rising body to completely overcome the Earth's attraction. Because of the independent action of the forces involved, a ball thrown horizontally or a projectile fired horizontally with velocity v will be accelerated downward at the same rate as a body falling from rest, regardless of the horizontal motion. At a sufficiently large horizontal velocity, a projectile would fall from the horizontal only at the same rate that the surface of the Earth curves away beneath it. The projectile would thus remain at the same elevation above the Earth and in effect become an Earth satellite. See Ballistics, Gravitation free fall Motion of a body under the influence of gravity alone, i.e. with no other forces acting. See also weightlessness.free fall[′frē ‚fȯl] (mechanics) The ideal falling motion of a body acted upon only by the pull of the earth's gravitational field. (petroleum engineering) In deep drilling, an arrangement by which the bit is permitted to fall freely to the bottom at each drop or down stroke. free fall1. The descent of freshly mixed concrete into forms without dropchutes or other means of confinement. 2. The distance through which such descent occurs. 3. The uncontrolled fall of aggregate.free fall A conventional free-fall bomb. Laser-guided bomb.i. Any jump in which the parachutist pulls his own ripcord.
ii. The fall or drop of a body, such as a rocket, not guided, not under thrust, and not retarded by a parachute or other braking device. free-fall bomb An unguided bomb that follows the rules of ballistics.free fall1. free descent of a body in which the gravitational force is the only force acting on it 2. the part of a parachute descent before the parachute opens AcronymsSeefoliosfree fall
Synonyms for free fallnoun the ideal falling motion of something subject only to a gravitational fieldRelated Wordsnoun a sudden sharp decrease in some quantitySynonymsRelated Words- decrement
- decrease
- correction
- voltage drop
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