These resources provide excellent illustrations of both relatively simple and very complex physical phenomena. The illustrations are clear and concise, showing important physical properties. The physics displayed is very difficult to illustrate accurately without tools such as these.
Users can control the physical parameters of the system to explore their impact. The three dimensional nature of these illustrations add to their power for developing conceptual models.
The systems simulated are both realistic and complicated, illustrating the power of the combination of physics and computation to predict the behavior of real systems. This moves the class beyond the simple, analytically solvable problems usually covered in introductory classes.