RED AND BLUE
Wait for the applet to fully load. Click on "blue ball", then on "(re)start" ...

blue ball    red ball       
For each ball: Where will the ball be after 20 seconds?
After what time is the ball at x = 36?

To model the motion, take readings from the animation - if you are unsure how, click HELP!
Make a table of the position of the ball after 0, 1, 2, 3, 4, ... seconds.

Is this motion linear or not? How can you find out?
Show that there is a common difference, or constant rate of change.
Find the formula for each animation in the form x(t) = at + b. Check that it fits the data!

Now use the formulas to answer the original questions:

Where is the blue ball after 20 seconds?   

Where is the red ball after 20 seconds?