We have shown that most students can be guided to change
how they think a force affects the acceleration of the centerof-
mass of a rigid body. We identified a particular case (the
block and spool context) in which previously identified conceptual
errors are very strongly elicited, and with which students
strongly associated their general ideas about the
relationship of forces to translational motion. This pivotal case
was not an experiment that was easily testable and many students
were not convinced by instructors’ claims about its outcome.
We also identified another case (the connected-spools
experiment) that, while testable, did not play a pivotal role in
student understanding of forces in combined rotational and
translational motion. That is, students remembered its outcome
but did not appreciate its significance. We developed a tutorial
that guides students to connect the pivotal case with the testable
case with various (correct and incorrect) theoretical perspectives
on the relationship between forces and combined
rotation and translation. As a result, students better understood
the meaning of experimental results that demonstrate the validity
of Newton’s second law and were able to apply this
understanding to concrete and more abstract contexts