**ACCELERATION**

**We are often interested in how fast the velocity is changing.
This is the acceleration.**

**Acceleration is a change of velocity divided by a change of
time so it has units of (meters/second)/second. We will write this as
m/s/s or m/s**^{2}. As with the velocity, we can describe the
average acceleration or we can describe the instantaneous
acceleration, the acceleration right now, at this particular
moment,

**As with the velocity, we will usually mean the instantaneous
acceleration if we simply say "the acceleration". We will often
restrict ourselves situations with a constant acceleration; in that
case the average acceleration is the same as the instantaneous
acceleration.**

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We can take the definition of acceleration, turn it around, and
write**
**If an objects starts at rest, so that v**_{i }= 0,
then

**The distance an accelerating object moves is**

**If an object starts at rest, so that v**_{i} = 0, and we
ask how far it travels, so x_{i} = 0, then

**
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**Consider a car that starts at rest and accelerates at 2 m/s/s
for 3 seconds.**

**At that time, t = 3 s, how fast is it going? and how far has it
gone?**

(C) 2003, Doug Davis; all rights reserved