Energy is a critical concept that is used in analyzing physical phenomena and is often an essential starting point in physics problem-solving. It is a global concept that appears throughout the physics curriculum in mechanics, thermodynamics, electromagnetism, and modern physics. Energy is also at the heart of descriptions of processes in biology, chemistry, astronomy, and geology. Therefore, it is important to discuss the topic of energy clearly and effectively in textbook and lecture presentations. Unfortunately, this topic is filled with possibilities for student confusion if the presentation is not carefully crafted by the instructor or the textbook. There are a number of steps, however, that can be taken in teaching about energy that reduce or eliminate the sources of confusion for students.
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As a textbook author myself, I do not specifically identify problematic statements in other authors' textbooks in this series of articles. I do not want this series to appear as a marketing tool but rather as a professional communication that offers a set of suggestions for improving the teaching of energy to our students. I present items from several textbooks in general terms and not as direct quotes.
14.
Full solutions to these two problems appear in J. W. Jewett, “Energy and the confused student V: The energy/momentum approach to problems involving rotating and deformable systems,” Phys. Teach., to be published in May 2008.
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J.W. Jewett, “Energy and the confused student II: Systems,” Phys. Teach., to be published in Feb. 2008.
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See, for example, R.A. Serway and J.W. Jewett, Physics for Scientists and Engineers, 7th ed. (Brooks/Cole, Belmont CA, 2008), pp. 204–209 or R.A. Serway and J.W. Jewett, Principles of Physics, 4th ed. (Brooks/Cole, Belmont CA, 2006), pp. 173–177.
19.
J.W. Jewett, “Energy and the confused student IV: A global approach to energy,” Phys. Teach., to be published in April 2008.
20.
This statement assumes that the surface applying the force is nondeformable. In reality, the surface will deform slightly; the ground depresses downward a bit when the boy jumps upward, the stairs or ladder rungs deform a small amount downward when the person climbs upward, the wall bends inward slightly when the girl pushes off or the putty slams into it. In these cases, the direction of the displacement of the point of application of the force is opposite that of the normal force exerted by the surface, so the work done on the boy, person, girl, or putty by the surface has a small negative value.
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© 2008 American Association of Physics Teachers.
2008
American Association of Physics Teachers
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