Research on problem-solving strategies has been conducted since the 1940s. Experts and novices use different strategies in problem solving; the main difference is in the familiarity with which they face new problems. For multiple-choice problems, an analysis of distractors can provide possible clues about the resolution processes developed by examination candidates and reveal some learning difficulties. Thus, this study analysed data from the Brazilian National High School Examination (ENEM) because it holds great importance at the national level and mobilizes millions of candidates due to its advantages, such as admission to high social demand courses in public universities in Brazil. Our main objective was to identify some of the difficulties high school graduates face in mechanical physics. Thus, we analysed the rate of alternatives for a sample of six million students, finding that practically all the mechanics items indicated that there was no priority model in the item resolution process. Considering this finding, we concluded that the mechanics items at ENEM could be deemed difficult to solve, also indicating a greater variety of errors that students comment on. To analyse these possible mistakes made by students, we applied the analysis on distractors, which represent the reasoning hypotheses that students make when solving an item incorrectly. The analysis revealed the existence of a large set of errors in the knowledge of these students, such as mathematical immediacy (40%), symbolic forms (22%), non-scientific conception (22%), intuitive reasoning (9%), and analysis of the wrong images provided by the item (9%).