1.the act of accelerating; increasing the speed
2.an increase in rate of change"modern science caused an acceleration of cultural change"
3.(physics) a rate of increase of velocity
AccelerationAc*cel`er*a"tion (�), n. [L. acceleratio: cf. F. accélération.] The act of accelerating, or the state of being accelerated; increase of motion or action; as, a falling body moves toward the earth with an acceleration of velocity; -- opposed to retardation.
A period of social improvement, or of intellectual advancement, contains within itself a principle of acceleration. I. Taylor.
(Astr. & Physics.) Acceleration of the moon, the increase of the moon's mean motion in its orbit, in consequence of which its period of revolution is now shorter than in ancient times. -- Acceleration and retardation of the tides. See Priming of the tides, under Priming. -- Diurnal acceleration of the fixed stars, the amount by which their apparent diurnal motion exceeds that of the sun, in consequence of which they daily come to the meridian of any place about three minutes fifty-six seconds of solar time earlier than on the day preceding. -- Acceleration of the planets, the increasing velocity of their motion, in proceeding from the apogee to the perigee of their orbits.
definition of Wikipedia
Academic acceleration • Acceleration (album) • Acceleration (education) • Acceleration Studies Foundation • Acceleration clause • Acceleration due to gravity • Acceleration due to gravity (disambiguation) • Acceleration of gravity • Acceleration onset cueing • Acceleration or deceleration lane • Acceleration radiation • Acceleration services • Aitken acceleration • Alaska Land Transfer Acceleration Act • Angular acceleration • Centrifugal Acceleration • Centripetal Acceleration • Centripetal acceleration • Cognitive acceleration • Compact wind acceleration turbine • Coriolis acceleration • DirectX Video Acceleration • Download acceleration • Fermi acceleration • Four-acceleration • Gal (acceleration) • Gravitational acceleration • Hardware acceleration • I/O Acceleration Technology • Laser wakefield acceleration • List of fastest cars by acceleration • List of international earthquake acceleration coefficients • Mortgage acceleration • Multimedia Acceleration eXtensions • Particle acceleration • Peak ground acceleration • Performance acceleration technology • Plasma acceleration • Proper acceleration • SSL acceleration • Sequence acceleration • Series acceleration • Spatial acceleration • Standard acceleration of gravity • Sudden unintended acceleration • Supernova / Acceleration Probe • Supernova/Acceleration Probe • TCP acceleration • Tidal acceleration • Uniform acceleration • Video Acceleration API • Video acceleration • Web page acceleration • Writ of acceleration • X-Video Bitstream Acceleration • XFree86 Acceleration Architecture
moteur thermique (fr)[Thème]
caractère, état, propriété (fr)[Classe...]
toute opération spécifique à un domaine (fr)[Classe...]
quicken; accelerate; speed; speed up; pick up speed[ClasseHyper.]
accelerate, quicken, speed, speedup, speed up - accelerate, pick up speed, quicken, speed, speed up - hurry, speed, travel rapidly, zip - speed - belt along, bucket along, cannonball along, flash, hasten, hie, hotfoot, pelt along, race, rush, rush along, speed, step on it, streak - rapid, speedy - hurrying, speed, speeding - acceleration, quickening, speedup - accelerator, butterfly valve, throttle, throttle valve - accelerator, accelerator pedal, gas, gas pedal, gun, throttle - celerity, fastness, rate, speed, swiftness, velocity - acceleration - speed, velocity - accelerative, acceleratory[Dérivé]
drive fast, speed[Cause]
acceleration; quickening; speedup[ClasseHyper.]
caractère d'un phénomène (fr)[ClasseParExt.]
conduite auto (fr)[DomaineCollocation]
opération de conduite d'un véhicule (fr)[DomaineCollocation]
hurrying, speed, speeding[Hyper.]
accelerate, pick up speed, quicken, speed, speed up[Nominalisation]
quicken; accelerate; speed; speed up; pick up speed[ClasseHyper.]
change - alter, change, vary - alter, change, modify - modify - hurrying, speed, speeding - acceleration, quickening, speedup - accelerator, butterfly valve, throttle, throttle valve - accelerator, accelerator pedal, gas, gas pedal, gun, throttle - celerity, fastness, rate, speed, swiftness, velocity - acceleration - speed, velocity - accelerative, acceleratory - decelerate, retard, slow, slow down, slow up - slack, slacken, slow, slow down, slow up - retard[Dérivé]
drive fast, speed[Cause]
decelerate, slow down[Ant.]
mathématiques appliquées (fr)[Classe]
physics; natural philosophy[ClasseHyper.]
natural philosophy, physics[Domaine]
|History of classical mechanics · Timeline of classical mechanics|
In physics, acceleration is the rate at which velocity changes with time. This change in velocity may be in magnitude, or direction, or both. In one dimension, acceleration is the rate at which something speeds up or slows down. For example, a car driving away (from standstill) is increasing its speed and is thus accelerating. Similarly, a car braking to stop in front of a traffic light is still said (in physics) to undergo acceleration, although now a negative one. In common speech, it is said to be decelerating. As acceleration is defined as how quickly velocity changes, it can be expressed as the change in velocity divided by the change in time , described by the formula:
As velocity has both a magnitude and direction (i.e. it is a vector quantity), thus acceleration is also a vector. As such, it describes the rate of change of both the magnitude (the speed) and the direction of velocity. This means that an object moving in a circular motion—such as a satellite orbiting the earth—is also accelerating, even though it may be moving at a constant speed. When an object is executing such a motion where it changes direction, but not speed, it is said to be undergoing centripetal (directed towards the center) acceleration. Oppositely, a change in the speed of an object, but not its direction of motion, is a tangential acceleration.
where F is the resultant force acting on the body, m is the mass of the body, and a is its acceleration.
Average acceleration is the change in velocity (Δv) divided by the change in time (Δt). Instantaneous acceleration is the acceleration at a specific point in time which is for a very short interval of time as Δt approaches zero. Acceleration can therefore be computed as the derivative (with respect to time) of velocity.
The velocity of a particle moving on a curved path as a function of time can be written as:
with v(t) equal to the speed of travel along the path, and
a unit vector tangent to the path pointing in the direction of motion at the chosen moment in time. Taking into account both the changing speed v(t) and the changing direction of ut, the acceleration of a particle moving on a curved path on a planar surface can be written using the chain rule of differentiation and the derivative of the product of two functions of time as:
where un is the unit (inward) normal vector to the particle's trajectory, and R is its instantaneous radius of curvature based upon the osculating circle at time t. These components are called the tangential acceleration and the radial acceleration or centripetal acceleration (see also circular motion and centripetal force).
Uniform or constant acceleration is a type of motion in which the velocity of an object changes by an equal amount in every equal time period.
A frequently cited example of uniform acceleration is that of an object in free fall in a uniform gravitational field. The acceleration of a falling body in the absence of resistances to motion is dependent only on the gravitational field strength g (also called acceleration due to gravity). By Newton's Second Law the force, F, acting on a body is given by:
Due to the simple algebraic properties of constant acceleration in the one-dimensional case (that is, the case of acceleration aligned with the initial velocity), there are simple formulas that relate the following quantities: displacement, initial velocity, final velocity, acceleration, and time:
In the case of uniform acceleration of an object that is initially moving in a direction not aligned with the acceleration, the motion can be resolved into two orthogonal parts, one of constant velocity and the other according to the above equations. As Galileo showed, the net result is parabolic motion, as in the trajectory of a cannonball, neglecting air resistance.
Uniform circular motion is an example of a body experiencing acceleration resulting in velocity of a constant magnitude but change of direction. In this case, because the direction of the object's motion is constantly changing, being tangential to the circle, the object's velocity also changes, but its speed does not. This acceleration is directed toward the centre of the circle and takes the value:
The acceleration, hence also the force acting on a body in uniform circular motion, is directed toward the center of the circle; that is, it is centripetal – the so called 'centrifugal force' appearing to act outward on a body is really a pseudo force experienced in the frame of reference of the body in circular motion, due to the body's linear momentum at a tangent to the circle.
"The force one feels from gravity and the force one feels from acceleration are the same. They are equivalent. Einstein called this the principle of equivalence. Since gravity and acceleration are equivalent, if you feel gravity's influence, you must be accelerating. Einstein argued that only those observers who feel no force at all - including the force of gravity - are justified in declaring that they are not accelerating."
|Wikimedia Commons has media related to: Acceleration|
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