Things to Understand about Average Velocity.

2. The average velocity during a given time interval is in general not equal to the arithmetic mean of the initial and final velocities.

Exercise. Display the Data boxes by pressing the Data button.

Set the ball's initial position, and release the mouse button. Click on the ball again, and continue to hold down the mouse button without dragging the ball. Observe that time is elapsing while the ball's velocity is clearly zero. Then drag the ball to a new position, still not releasing the mouse button. More time is elapsing while the ball is again at rest and its velocity zero once more. Release the mouse button.

Observe that the applet shows the average velocity to be unequal to zero (unless your displacement happens to be zero) while the mean of the initial and final velocities, which are both zero, clearly is zero. The non-zero value is correct because it results from the definition of average velocity on Page 2 with a non-zero displacement. Average velocity is not defined as the arithmetic mean of the initial and final velocity..

You may want to review the analogous situation for average speed under Speed/Average/Explain It. There you will find more information about the kind of average involved in both average speed and average velocity.