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machanics

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  • andreakarenreataza_20
    Acceleration From Wikipedia, the free encyclopedia. Jump to: navigation, search Acceleration is the time rate of change of velocity, and at any point on a v-t
    Message 1 of 2 , Dec 1, 2005
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      Acceleration
      From Wikipedia, the free encyclopedia.
      Jump to: navigation, search

      Acceleration is the time rate of change of velocity, and at any point
      on a v-t graph, it is given by the gradient of the tangent to that
      pointIn physics, acceleration (symbol: a) is defined as the rate of
      change (or time derivative) of velocity. It is thus a vector quantity
      with dimension length/time². In SI units, this is meter/second².

      Contents [hide]
      1 Explanation
      2 Relation to relativity
      3 References
      4 External links and references



      [edit]
      Explanation
      To accelerate an object is to change its velocity over a period of
      time. In this strict scientific sense, acceleration can have positive
      and negative values – respectively called acceleration and
      deceleration (or retardation) in common speech – as well as change of
      direction. Acceleration is defined technically as "the rate of change
      of velocity of an object with respect to time" and is given by the
      equation


      where

      a is the acceleration vector
      v is the velocity vector expressed in m/s
      t is time expressed in seconds.
      This equation gives a the units of m/(s·s), or m/s² (read as "metres
      per second per second", or "metres per second squared").

      An alternative equation is:


      where

      â is the average acceleration (m/s²)
      u is the initial velocity (m/s)
      v is the final velocity (m/s)
      t is the time interval (s)
      Transverse acceleration (perpendicular to velocity) causes change in
      direction. If it is constant in magnitude and changing in direction
      with the velocity, we get a circular motion. For this centripetal
      acceleration we have


      One common unit of acceleration is g, one g being the acceleration
      caused by the gravity of Earth at sea level at 45° latitude (Paris),
      or about 9.81 m/s².

      Accelerating acceleration or jerk is the rate of change of an
      object's acceleration over time.

      In classical mechanics, acceleration is related to force and mass
      (assumed to be constant) by way of Newton's second law:


      As a result of its invariance under the Galilean transformations,
      acceleration is an absolute quantity in classical mechanics.

      [edit]
      Relation to relativity
      After defining his theory of special relativity, Albert Einstein
      realized that forces felt by objects undergoing constant acceleration
      are indistinguishable from those in a gravitational field, and thus
      defined general relativity that also explained how gravity's effects
      could be limited by the speed of light.

      If you accelerate away from your friend, you could say (given your
      frame of reference) that it is your friend who is accelerating away
      from you, although only you feel any force. This is also the basis
      for the popular Twin paradox, which asks why only one twin ages when
      moving away from his sibling at near light-speed and then returning,
      since the 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. With changing velocity, accelerated objects exist in
      warped space (as do those that reside in a gravitational field).
      Therefore, frames of reference must include a description of their
      local spacetime curvature to qualify as complete.

      Acceleration can be measured using an accelerometer.
    • santos_erhs
      study of energy and forces: the branch of physics and mathematics that deals with the effect of energy and forces on systems
      Message 2 of 2 , Jan 18, 2007
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        study of energy and forces: the branch of physics and mathematics that
        deals with the effect of energy and forces on systems
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