Position-Velocity Relationship
For one-dimensional motion, the velocity of the object at any given time is equal to the slope of the position vs. time graph at that particular time. Each time you click "Go" you get two graphs, showing the position and velocity of an object as functions of time. Repeatedly clicking "Step" takes you through a series of points on the position graph along with the corresponding points on the velocity graph. You should carefully note the relationship between (the slope of) the position and the velocity at each time.