Acceleration is defined as the rate of change of velocity. . When an object is moving faster there is a positive acceleration and when it is moving slower there is a negative acceleration. Because velocity is a vector quantity, acceleration is also a vector quantity. Acceleration occurs when an object changes direction. The SI unit for acceleration is m/s/s or m/s2. Acceleration can be described by the following :
where vf is the final velocity and vi is the initial velocity. The change in time is usually expressed as simply t because you assume that the initial time was zero. Some definitions follow:
Uniform acceleration
constant, unchanging acceleration; when an object is
uniformly accelerated, the speed of the entire time interval that the
acceleration occurred over can be represented by the average velocity of that
time interval.
Variable acceleration
non-uniform acceleration. For our purposes, we
assume that acceleration is uniform.
Positive acceleration
velocity of object increases
Negative acceleration (or deceleration)
velocity of object decreases
Average acceleration
the change in velocity divided by the time taken to
make this change
Acceleration due to gravity (or g)
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