Clarify the inconsistent law selections of individual students

Investigate why a student who appeared to use Newton’s Second Law and Newton’s Third Law inconsistently across the car–truck questions selected Newton’s Third Law alongside Newton’s Second Law for Question 15 and Newton’s First Law alongside Newton’s Second Law for Question 16.

Background

The study supplements answers to Force Concept Inventory Questions 15 and 16 with law-selection sub-questions. For one illustrative student, the responses suggested confusion between force and acceleration, while the selected laws did not consistently match the apparent reasoning in the answers. The authors identify the reason for this mismatch as unresolved and suggest that interviews could provide further insight into unclear free-text responses.