This applet is adapted from Luke's work at http://tube.geogebra.org/material/show/id/99320# Intended for students to visualize the concept of speed as distance per unit time and to learn basic calculations of the 3rd quantity if given the other two.
This files is downloadable from Geogebra Tube at http://tube.geogebra.org/material/show/id/N9cWPaX6
The applet can help you to understand speed as a rate : It is the distance travelled per unit of time. In the applet, unit for time is seconds, and unit for distance is metres.
NOTE : The speed of the red and blue car is fixed