This invited talk shows how the Tracker video analysis and modeling program enables students to create particle model simulations based on Newton's laws and to compare their behavior directly with that of real-world objects captured on video. Tracker's "model builder" provides a gentle introduction to dynamic modeling by making it easy to define and modify force expressions, parameter values and initial conditions while hiding the numerical algorithm details. Because the model simulations synchronize with and draw themselves right on the video, students can test their models experimentally by direct visual inspection, a process that is both intuitive and discerning. A digital library browser enables users to open videos and models directly from web-based collections such as the ComPADRE National Science Digital Library.