In recent years there has been an increasing interest in mathematics teaching and learning at undergraduate level. However, many fields are little explored; differential equations being one of these topics. In this study I use the theoretical framework of Coordination Classes to analyze how undergraduate mechanical engineering students apply their knowledge in the context of system dynamics and what resources and strategies they used; in this subject, students model dynamics systems based on Ordinary Differential Equations (ODEs). I applied three tasks in different contexts (Mechanical, Electrical and Fluid Systems) in order to identify what information was relevant for the students, readout strategies; what inferences students made with the relevant information, causal nets; and what strategies students used to apply their knowledge in those contexts, concept projections. I found that the core problem at projecting their knowledge relied on the causal nets, coinciding with diSessa and Wagner's conjecture (2005). I also identified and characterized three strategies or concept projections students used in solving the tasks: Diagram-based approach, Component-based approach and Equation-based approach.