BOX 6.2 How Do You Know?

A 1-kilogram stick that is 2 meters long is placed on a frictionless surface and is free to rotate about a vertical pivot through one end. A 50-gram lump of putty is attached 80 centimeters from the pivot. Which of the following principles would allow you to determine the magnitude of the net force between the stick and the putty when the angular velocity of the system is 3 radians/second?

  1. Newton’s second law,

  2. Angular momentum or conservation of angular momentum

  3. Linear momentum or conservation of linear momentum

  4. Work-energy theorem or conservation of mechanical energy

  5. Conservation of linear momentum followed by conservation of mechanical energy

Performance on this item was near random for students finishing an introductory calculus-based physics course. The temptation is to match the “rotation” surface feature of the problem with “angular momentum,” when in fact the problem is solved by a simple application of Newton’s second law. Data such as these are important for helping teachers guide students toward the development of fluid, transferable knowledge (Leonard et al., 1996).

provide a framework for integrating cognition and context in assessing achievement in science. In their report, performance is described in terms of the content and process task demands of the subject matter and the nature and extent of cognitive activity likely to be observed in a particular assessment situation. The framework provides a basis for examining how developers’ intentions are realized in performance assessments that purport to measure reasoning, understanding, and complex problem solving.

Characterizing assessments in terms of components of competence and the content-process demands of the subject matter brings specificity to generic assessment objectives such as “higher level thinking and deep understanding.” Characterizing student performance in terms of cognitive activities focuses attention on the differences in competence and subject-matter achievement that can be observed in learning and assessment situations. The kind and quality of cognitive activities in an assessment is a function of the content and process demands of the task involved. For example, consider the content-process framework for science assessment shown in Figure 6.2 (Baxter and Glaser, 1997). In this figure, task demands for content

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