Things to Understand about Average Velocity.

1. Average velocity is not the same as average speed.

• Average velocity is a vector and has direction. Average speed is a scalar and does not have direction.
• The magnitude of the average velocity, which is a scalar, is not equal to the average speed in general.

Exercise (to illustrate the second bullet). For the average velocity obtained in the Exercise on Page 2, calculate the magnitude |_av| of the average velocity using the components v_x,av and v_y,av and the Pythagorean formula,

Compare this magnitude to the average speed, v_av. Is it equal to, less than or greater than the average speed? Can you explain the numbers you observe?

The magnitude of the average velocity is in general different from the average speed. Therefore, we must use different symbols for the two quantities. The notation v_av is used only for average speed while the more elaborate notation |_av| is used for the magnitude of the average velocity.