Difference between revisions of "Acceleration"
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| − | + | Acceleration is the rate of change of an object's [[velocity]].<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref>. More precisely, it is defined as the derivative of [[velocity]] over time, and is a vector. For an object to undergo an acceleration, a [[force]] needs to be exerted on the object. An example is a falling object on [[Earth]], which is subject to a [[gravity|gravitational force]]. The resulting acceleration ''g'' is independent of the mass of the object, and is approximately 9.81 [[meters]] per [[second]] per [[second]] near the Earth's surface<ref>Marcelo Alonso and Edward J. Finn, ''Fundamental University Physics'', Addison-Wesley.</ref>. | |
| − | + | According to Newton's Second Law of Motion, calculation of acceleration is done with the formula <math>\vec F=m \vec a</math>, where F=force and is measured in Newtons, m=mass and is measured in kilograms, and a=acceleration and is measured in meters per second squared. Using the formula we can find that <math> \vec a=\frac{\vec F}{m}</math>. | |
| − | + | In the case of straight trajectory, if an object's acceleration and [[velocity]] have the same sign, the object is gaining [[speed]]. If acceleration and velocity have different signs, the object is losing speed. If [[velocity]] is [[zero]], acceleration is not necessarily zero. If acceleration is zero, velocity is not necessarily zero. | |
| − | + | In case of a curvilinear trajectory, there is an acceleration, even if speed is constant. | |
==References== | ==References== | ||
Revision as of 13:09, November 8, 2007
Acceleration is the rate of change of an object's velocity.[1]. More precisely, it is defined as the derivative of velocity over time, and is a vector. For an object to undergo an acceleration, a force needs to be exerted on the object. An example is a falling object on Earth, which is subject to a gravitational force. The resulting acceleration g is independent of the mass of the object, and is approximately 9.81 meters per second per second near the Earth's surface[2].
According to Newton's Second Law of Motion, calculation of acceleration is done with the formula 
, where F=force and is measured in Newtons, m=mass and is measured in kilograms, and a=acceleration and is measured in meters per second squared. Using the formula we can find that 
.
In the case of straight trajectory, if an object's acceleration and velocity have the same sign, the object is gaining speed. If acceleration and velocity have different signs, the object is losing speed. If velocity is zero, acceleration is not necessarily zero. If acceleration is zero, velocity is not necessarily zero.
In case of a curvilinear trajectory, there is an acceleration, even if speed is constant.
