Changes

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>.

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 the case of straight trajectory, if an object's acceleration and [[velocity]] have the same direction, the object is gaining [[speed]].  If the acceleration and velocity have opposite directions, the object is losing speed. If the acceleration is zero, then the object is either at rest or travelling in a straight line at constand speed.

In case of a curvilinear trajectory, there is an acceleration, even if speed is constant.

In case of a curvilinear trajectory, there is an acceleration, even if the speed of the object is constant.  This is because the ''direction'' of the object's velocity changes if the path is curved.  And whenever there is a change in velocity, there is an acceleration, since acceleration is the change in velocity with respect to time.

==References==

==References==