# Dictionary Definition

accelerating adj : increasing in speed; becoming
progressively faster; "the accelerating inflation was cause for
great concern"

# User Contributed Dictionary

## English

### Verb

accelerating- present participle of accelerate

# 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.)## Formula

The formula for the average acceleration over a time period \Delta t is- \mathbf=\frac

- \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

- \mathbf(t)=\lim_\frac=\frac

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:

- \bar\int_^\mathrmt=\int_^\mathbf(t)\mathrmt

Putting it all together means:

- \mathbf = \frac = \frac

- \mathbf is acceleration
- \mathbf is velocity
- \mathbf is position
- is time

## See also

## External links

- Acceleration and Free Fall - a chapter from an online textbook
- Trajectories and Radius, Velocity, Acceleration on Project PHYSNET (ERROR - PAGE MOVED)
- Science aid: Movement
- Physics Classroom: Acceleration
- Science.dirbix: Acceleration
- Acceleration Calculator
- Motion Characteristics for Circular Motion

accelerating in Afrikaans: Versnelling

accelerating in Arabic: تسارع

accelerating in Asturian: Aceleración

accelerating in Bengali: ত্বরণ

accelerating in Min Nan: Ka-sok-tō͘

accelerating in Belarusian: Паскарэнне

accelerating in Bosnian: Ubrzanje

accelerating in Bulgarian: Ускорение

accelerating in Catalan: Acceleració

accelerating in Czech: Zrychlení

accelerating in Welsh: Cyflymiad

accelerating in Danish: Acceleration

accelerating in German: Beschleunigung

accelerating in Estonian: Kiirendus

accelerating in Modern Greek (1453-):
Επιτάχυνση

accelerating in Spanish: Aceleración

accelerating in Esperanto: Akcelo

accelerating in Basque: Azelerazio

accelerating in Persian: شتاب

accelerating in French: Accélération

accelerating in Irish: Luasghéarú

accelerating in Manx: Bieauaghey

accelerating in Galician: Aceleración

accelerating in Hakka Chinese: Kâ-suk-thu

accelerating in Korean: 가속도

accelerating in Croatian: Ubrzanje

accelerating in Ido: Acelero

accelerating in Indonesian: Percepatan

accelerating in Icelandic: Hröðun

accelerating in Italian: Accelerazione

accelerating in Hebrew: תאוצה

accelerating in Latin: Acceleratio

accelerating in Latvian: Paātrinājums

accelerating in Lithuanian: Pagreitis

accelerating in Hungarian: Gyorsulás

accelerating in Malayalam: ത്വരണം

accelerating in Malay (macrolanguage):
Pecutan

accelerating in Mongolian: Хурдатгал

accelerating in Dutch: Versnelling
(natuurkunde)

accelerating in Japanese: 加速度

accelerating in Norwegian: Akselerasjon

accelerating in Norwegian Nynorsk:
Akselerasjon

accelerating in Novial: Akseleratione

accelerating in Polish: Przyspieszenie

accelerating in Portuguese: Aceleração

accelerating in Quechua: P'ikwachiy

accelerating in Russian: Ускорение

accelerating in Sicilian: Accilirazzioni

accelerating in Simple English:
Acceleration

accelerating in Slovak: Zrýchlenie

accelerating in Slovenian: Pospešek

accelerating in Serbian: Убрзање

accelerating in Serbo-Croatian: Ubrzanje

accelerating in Finnish: Kiihtyvyys

accelerating in Swedish: Acceleration

accelerating in Telugu: త్వరణము

accelerating in Thai: ความเร่ง

accelerating in Vietnamese: Gia tốc

accelerating in Turkish: İvme

accelerating in Ukrainian: Прискорення

accelerating in Chinese: 加速度