Dynamic Model—Friction on Ice Now that you know how forces affect the motions of objects, you can use the Tracker video analysis tool to create dynamic models for a wide range of physical situations.

Tracker enables you to create two different types of mathematical models: analytical and dynamic. An analytical model enables you to enter mathematical expressions for x and y positions as a function of time. That’s sometimes useful, but from a physics perspective, a dynamic model is much more flexible and powerful.

A dynamic model enables you to set the initial conditions for a particular system (initial positions and velocities); then you can mathematically define any forces acting on that system. Once those are set up, the model acts like an object in space, responding to the forces you’ve imposed on it. It can continue moving forever, if that’s what the forces would do to an object in real life. By visually matching a marker for your model to the r