Temple University: Gerardo Mendoza and Dan Reich's "Calculus on the Web"
Click the link to Book I, and click on the "Index" button. Click on button 5 (Distance) to launch the first module. Complete problems 1-5. Then, return to the index and click on button 8 (Circles II) to launch the other module. Complete problems 1-5. If at any time the problem set becomes too easy for you, feel free to move on.