 | Acceleration: Encyclopedia II - Acceleration - Explanation
Acceleration - Explanation
To accelerate an object is to change its velocity in relation to time. In this strict scientific sense, acceleration can have positive and negative values – respectively called acceleration (velocity is increased) and deceleration (or retardation -- velocity is decreased) in common speech – as well as change of direction. Acceleration is a vector defined by properties of magnitude (size or measureabililty) and direction. When either speed or direction are changed, there is a change in acceleration.
Acceleration is defined technically as "the rate of change of velocity of an object with respect to time" and the instantaneous acceleration of an objection is given by the equation
where
a is the acceleration vector (as acceleration is a vector, it must be described with both a direction and a magnitude.
v is the velocity vector
t is time
When velocity is plotted against time on a velocity vs. time graph, the acceleration is given by the slope, or the derivative of the graph.
If used with SI standard units (meters per second for velocity; seconds for time) 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 average acceleration, or acceleration over time, ā can be defined as:
where
u is the initial velocity (m/s)
v is the final velocity (m/s)
t is the time interval (s) elapsed between the two velocity measurements
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.
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.
Other related archivesAlbert Einstein, Differentiate, Displacement, Earth, Galilean transformations, General relativity, Integrate, Jerk, Kinematics, Newton's second law, SI, SI units, Speed, Transverse, Twin paradox, Velocity, accelerometer, centripetal acceleration, circular motion, classical mechanics, curvature, derivative, direction, force, g, general relativity, gravity, inertial frames of reference, invariance, latitude, length, light, magnitude, mass, metre/second², perpendicular, physics, sea, spacetime, special relativity, time, vector, velocity, velocity vs. time graph
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