AskDefine | Define acceleration

Dictionary Definition



1 an increase in speed; "modern science caused an acceleration of cultural change" [ant: deceleration]
2 the act of accelerating; increasing the speed [syn: quickening, speedup]
3 (physics) a rate of change of velocity

User Contributed Dictionary




  • əksĕlərā'shən, /ək.sɛl.əˈreɪ.ʃən/, /@ksEl@"reIS@n/
    Rhymes: -eɪʃǝn


  1. (uncountable) The act of accelerating, or the state of being accelerated; increase of motion or action; as opposed to retardation or deceleration.
    a falling body moves toward the earth with an acceleration of velocity
  2. (countable) The amount by which a speed or velocity increases (and so a scalar quantity or a vector quantity).
    The boosters produce an acceleration of 20 metres per second per second.
    A period of social improvement, or of intellectual advancement, contains within itself a principle of acceleration — I. Taylor
  3. The change of velocity with respect to time (can include deceleration or changing direction).

Usage notes

Acceleration in SI units is measured in metres per second per second (m/s2), or in imperial units in feet per second per second (ft/s2).



act, state
  • Croatian: akceleracija, ubrzanje
  • Czech: zrychlení
  • Dutch: versnelling, acceleratie
  • Finnish: kiihdytys
  • French: accélération
  • German: Beschleunigung
  • Hebrew: האצה (he'atza)
  • Interlingua: acceleration
  • Italian: accelerazione
  • Japanese: 加速 (かそく, kasoku)
  • Norwegian: akselerasjon
  • Polish: przyspieszenie, akceleracja
  • Portuguese: aceleração
  • Romanian: acceleraţie
  • Russian: ускорение, разгон
  • Spanish: aceleración
  • Swedish: acceleration
  • Croatian: akceleracija, ubrzanje
  • Czech: zrychlení
  • Dutch: versnelling, acceleratie
  • Finnish: kiihtyvyys
  • French: accélération
  • German: Beschleunigung
  • Hebrew: תאוצה (teutza)
  • Italian: accelerazione
  • Japanese: 加速度 (かそくど, kasokudo)
  • Polish: przyspieszenie
  • Swedish: acceleration
  • Croatian: akceleracija, ubrzanje
  • Czech: zrychlení
  • Dutch: versnelling, acceleratie
  • Finnish: kiihtyvyys
  • French: accélération
  • German: Beschleunigung
  • Hebrew: תאוצה
  • Italian: accelerazione
  • Polish: przyspieszenie
  • Russian: ускорение
  • Slovene: pospešek
  • Swedish: acceleration
  • Urdu: اسراع (israa)



  1. acceleration



  1. acceleration; a change in velocity

Extensive Definition

In physics, acceleration is defined as the rate of change of velocity, or as the second derivative of position (with respect to time). It is then a vector quantity with dimension length/time². In SI units, acceleration is measured in meters/second² (m·s-2). The term "acceleration" generally refers to the rate of change in instantaneous velocity. (velocity is speed and direction)
In common speech, the term acceleration is only used for an increase in speed; a decrease in speed is called deceleration. In physics, any increase or decrease in speed is referred to as acceleration and similarly, motion in a circle at constant speed is also an acceleration, since the direction component of the velocity is changing. See also Newton's Laws of Motion.

Relation to relativity

After completing his theory of special relativity, Albert Einstein realized that forces felt by objects undergoing constant proper acceleration are indistinguishable from those in a gravitational field. This was the basis for his development of general relativity, a relativistic theory of gravity. This is also the basis for the popular Twin paradox, which asks why one twin ages less when moving away from his sibling at near light-speed and then returning, since the non-aging twin can say that it is the other twin that was moving. General relativity solved the "why does only one object feel accelerated?" problem which had plagued philosophers and scientists since Newton's time (and caused Newton to endorse absolute space). In special relativity, only inertial frames of reference (non-accelerated frames) can be used and are equivalent; general relativity considers all frames, even accelerated ones, to be equivalent. (The path from these considerations to the full theory of general relativity is traced in the Introduction to general relativity.)


The formula for the average acceleration over a time period \Delta t is
\mathbf(t+\Delta t) is the final velocity
\mathbf(t) is the initial velocity
\mathbf is the initial time and \Delta \mathbf is the change in time
The formula for the instantaneous acceleration at time t is
Thus acceleration is the first derivative of velocity. One should note that the expression (Final position - Initial Position) / (Total time taken) is the average velocity, and the limit as the time interval approaches zero is the instantaneous velocity. Therefore, velocity is the first derivative of position, making acceleration the second.
One should also note that the average and instantaneous accelerations over a time period \Delta t=t_1-t_0 are related through the Mean Value Theorem for Integrals:
Putting it all together means:
\mathbf = \frac = \frac
\mathbf is acceleration
\mathbf is velocity
\mathbf is position
is time
acceleration in Afrikaans: Versnelling
acceleration in Arabic: تسارع
acceleration in Asturian: Aceleración
acceleration in Bengali: ত্বরণ
acceleration in Min Nan: Ka-sok-tō͘
acceleration in Belarusian: Паскарэнне
acceleration in Bosnian: Ubrzanje
acceleration in Bulgarian: Ускорение
acceleration in Catalan: Acceleració
acceleration in Czech: Zrychlení
acceleration in Welsh: Cyflymiad
acceleration in Danish: Acceleration
acceleration in German: Beschleunigung
acceleration in Estonian: Kiirendus
acceleration in Modern Greek (1453-): Επιτάχυνση
acceleration in Spanish: Aceleración
acceleration in Esperanto: Akcelo
acceleration in Basque: Azelerazio
acceleration in Persian: شتاب
acceleration in French: Accélération
acceleration in Irish: Luasghéarú
acceleration in Manx: Bieauaghey
acceleration in Galician: Aceleración
acceleration in Hakka Chinese: Kâ-suk-thu
acceleration in Korean: 가속도
acceleration in Croatian: Ubrzanje
acceleration in Ido: Acelero
acceleration in Indonesian: Percepatan
acceleration in Icelandic: Hröðun
acceleration in Italian: Accelerazione
acceleration in Hebrew: תאוצה
acceleration in Latin: Acceleratio
acceleration in Latvian: Paātrinājums
acceleration in Lithuanian: Pagreitis
acceleration in Hungarian: Gyorsulás
acceleration in Malayalam: ത്വരണം
acceleration in Malay (macrolanguage): Pecutan
acceleration in Mongolian: Хурдатгал
acceleration in Dutch: Versnelling (natuurkunde)
acceleration in Japanese: 加速度
acceleration in Norwegian: Akselerasjon
acceleration in Norwegian Nynorsk: Akselerasjon
acceleration in Novial: Akseleratione
acceleration in Polish: Przyspieszenie
acceleration in Portuguese: Aceleração
acceleration in Quechua: P'ikwachiy
acceleration in Russian: Ускорение
acceleration in Sicilian: Accilirazzioni
acceleration in Simple English: Acceleration
acceleration in Slovak: Zrýchlenie
acceleration in Slovenian: Pospešek
acceleration in Serbian: Убрзање
acceleration in Serbo-Croatian: Ubrzanje
acceleration in Finnish: Kiihtyvyys
acceleration in Swedish: Acceleration
acceleration in Telugu: త్వరణము
acceleration in Thai: ความเร่ง
acceleration in Vietnamese: Gia tốc
acceleration in Turkish: İvme
acceleration in Ukrainian: Прискорення
acceleration in Chinese: 加速度

Synonyms, Antonyms and Related Words

accelerando, aggravation, beefing-up, blowing up, blowup, concentration, condensation, consolidation, deepening, double time, double-quick, double-quick time, drive, enhancement, exacerbation, exaggeration, explosion, festination, forced march, forwarding, getaway, hastening, heating-up, heightening, hurrying, impetus, information explosion, intensification, magnification, pickup, population explosion, quickening, redoubling, reinforcement, speeding, speedup, step-up, strengthening, thrust, tightening
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