The aim of this teaching experiment, which was performed with first-year engineering students at a technical institute, was to teach the force concept in a new way. In general, the research was based on constructivism and, especially, the planning of the new course was based on constructivism research into students' learning. As expected, the new course helped students to understand the interaction idea of the force concept, whereas the idea of relating force to motion remained common even after the course. In general, the results reinforce the importance of the teacher's awareness of students' preconceptions.