The drill problems can repeat themselves. Having a few more different examples might be useful.
This will not replace a textbook. The physical quantities (displacement, velocity, etc.) are not sufficiently defined for this material to stand on its own.
Active learning will be harder to encourage without automatic grading and due date enforcement. There will also need to be other aspects of the course that use the lessons learned with this tool to reinforce the lessons' importance and to make students remain attentive while using the tool.