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**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} (there are **no** "square
seconds")**. 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,**

**This, too, is a derivative,**

**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**
**The distance an accelerating object moves is**

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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) 2002, Doug Davis; all rights
reserved