The purpose of this article was to examine the effectiveness of a lesson plan to promote the application of the rule of composition and decomposition of force in science lessons at a junior high school. The lesson plan aimed to (1) incorporate the operational rules and “converse-type questions”, and (2) clarify the differences and similarities between composition rules and decomposition rules by using super-ordinate rules. The effectiveness of the lesson plan was evaluated based on post-evaluation tasks and lesson process. The analysis of 83 third graders in junior high school showed that, with the exception of certain problems, in the post-evaluation tasks the rate of correct responses was around 50%. Moreover, the incorrect responses indicated a confusion between the composition rule and the decomposition rule. The analysis of the teaching-learning process showed that these results would had been caused by “converse-type questions” and the lack of teacher’s explanation of hierarchical relationships between the super and sub-ordinate rules, as well as the lack of teacher questions concerning the overall consequences of the rule statements.
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