Motivated by the benefits of repeated deliberate practice, we created an interactive exercise system for use in an undergraduate engineering mechanics class that focuses on practicing learned fundamental concepts. These exercises take the form of traditional word problems commonly found in mechanics courses, involving things like selecting and solving the correct equations. They are automatically graded, and the system provides targeted feedback that identifies errors in student solutions. To evaluate the success of the design of our interface and the feedback engine, we conducted usability studies with students in two offerings of an engineering mechanics course in Fall 2020 and Spring 2021. We also surveyed instructors teaching similar course content at other universities to evaluate our system. Our instructor survey collected input on what features they feel would be pedagogically useful based on their experiences teaching similar courses. Our studies showed instructors and students liked the core interface design, and instructors found the system easy to learn. However, students and instructors requested improved interface intuitiveness and usability in general, with specific requests for flexibility in equation inputs and workspace management. Students and instructors favored the feedback system in general, with students expressing mixed reviews, and instructors expressing concerns that too much feedback could interfere with learning. We use these findings to provide an outline for future development plans for this system.