Physical design projects are a way to motivate and engage students in authentic science and engineering practices. Web-based tools can support design projects to ensure that students address and reflect upon critical science concepts during the course of the project. In addition, by specifying challenging design goals that require students to consider potential trade-offs between features, web-based tools may promote more deliberative scientific inquiry than open-ended or feature maximization goals. To study the role of web-supported projects, we developed an online curriculum that guides students through the planning, building, and analysis of self-propelled vehicles. To address content related to energy transformation we incorporated virtual models that display dynamic graphs of energy levels as a virtual scooter travels along a path. We compared two design goals for the project with different constraints. In the "target" version students are prompted to build virtual and physical scooters to reach a specific position. In the "distance" version students are prompted to maximize the distance the scooter travels. Our results indicate that students learned energy concepts from both versions; however, students with the "target" version did refer to the virtual model in their posttest responses to a greater degree than those with the "distance" version.