from negative to positive, yet it is accelerating at this moment since its velocity is
changing.
ǻv = change in instantaneous velocity
ǻt = elapsed time
Units: meters per second squared
(m/s^2 )
What is the average acceleration
of the mouse between 2.5 and
4.5 seconds?
2.9 - Average acceleration
Average acceleration: The change in
instantaneous velocity divided by the elapsed
time.
Average acceleration is the change in instantaneous velocity over a period of elapsed
time. Its definition is shown in Equation 1 to the right.
We will illustrate average acceleration with an example. Let's say you are initially driving
a car at 12 meters per second and 8 seconds later you are moving at 16 m/s. The
change in velocity is 4 m/s during that time; the elapsed time is eight seconds. Dividing
the change in velocity by the elapsed time determines that the car accelerates at an
average rate of 0.5 m/s^2.
Perhaps the car's acceleration was greater during the first four seconds and less during
the last four seconds, or perhaps it was constant the entire eight seconds. Whatever the
case, the average acceleration is the same, since it is defined using the initial and final
instantaneous velocities.
Average acceleration
Change in instantaneous velocity
divided by elapsed time
(^32) Copyright 2000-2007 Kinetic Books Co. Chapter 02