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Classroom response systems (CRSs) can be potent tools for teaching physics. Their efficacy, however, depends strongly on the quality of the questions used. Creating effective questions is difficult, and differs from creating exam and homework problems. Every CRS question should have an explicit pedagogic purpose consisting of a content goal, a process goal, and a metacognitive goal. Questions can be engineered to fulfil their purpose through four complementary mechanisms: directing students' attention, stimulating specific cognitive processes, communicating information to instructor and students via CRS-tabulated answer counts, and facilitating the articulation and confrontation of ideas. We identify several tactics that help in the design of potent questions, and present four "makeovers" showing how these tactics can be used to convert traditional physics questions into more powerful CRS questions.

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Classroom response systems (CRSs) are a promising instructional technology, but most literature on CRS use fails to distinguish between technology and pedagogy, to define and justify a pedagogical perspective, or to discriminate between pedagogies. Technology-enhanced formative assessment (TEFA) is our pedagogy for CRSbased science instruction, informed by experience and by several traditions of educational research. In TEFA, four principles enjoin the practice of question-driven instruction, dialogical discourse, formative assessment, and metalevel communication. These are enacted via the question cycle, an iterative pattern of CRS-based questioning that can serve multiple instructional needs. TEFA should improve CRS use and help teachers ''bridge the gap'' between educational research findings and practical, flexible classroom strategies for science instruction.

Two new independent mass relations are derived and are shown to be consistent with several existing nuclear models. The most general functional dependence on proton number, neutron number, and mass number (or isospin value) of masses which satisfy these relations exactly is discussed, and a procedure for determining the values of these functions which give a best least-squares fit to the body of known masses is developed. The functions which give the best over-all fit are listed together with the resulting theoretical mass table which shows the discrepancies to known masses and the theoretical values for proton, neutron, and alpha-particle decay energies.

We present a teaching strategy to encourage flexible, non algorithmic problem solving. Students create several problem representations to answer questions about a single problem situation. Through reflection students learn the value of non algebraic representations for analyzing and solving physics problems.

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Beginning physics students were constrained to analyze mechanics problems according to a hierarchical scheme that integrated concepts, principles, and procedures. After five 1‐hour sessions students increased their reliance on the use of principles in categorizing problems according to similarity of solution and in writing qualitative explanations of physical situations. In contrast, no consistent shift toward these expert‐like competencies was observed using control treatments in which subjects spent the same amount of time solving problems using traditional approaches. In addition, when successful at performing the qualitative analyses, novices showed significant improvements in problem‐solving performance in comparison to novices who directed their own problem‐solving activities. The implications of this research are discussed in terms of instructional strategies aimed at promoting a deeper understanding of physics.