Learning Goal: To practice finding the acceleration vector
Suppose an object has an initial velocity at time and later, at time , has velocity . The fact that the velocity changes tells us the object undergoes an acceleration during the time interval . From the definition of average acceleration,
we see that the acceleration vector points in the same direction as the vector . This vector is the change in the velocity , so to know which way the acceleration vector points, we have to perform the vector subtraction . This problem shows how to use vector subtraction to find the acceleration vector.
Finding the acceleration Vector
To find the acceleration as the velocity changes from to :

 Draw the velocity vector
2. Draw at the tip of
3. Draw . This is the direction of
4. Return to the original motion diagram. Draw a vector at the middle point in the direction of ; label it . This is the average acceleration at the midpoint between and