Energy and the Confused Student III: Language - Loreto-Unican

situation, but it is not true in general. This type of absolutestatement that does not refer to the conditionsshould be avoided because it leads students to believethat, in this case, the work-kinetic energy theorem is afundamental principle. While the statement is true fora situation in which a horizontal force is applied to anobject on a horizontal frictionless surface, it becomesfalse when the surface has friction or in any case inwhich the work done on a system does not result ina change in the speed, such as lifting a book from alower shelf and placing it on a higher shelf.ConclusionThere are many places where we can lead ourstudents into misinterpretations by careless use oflanguage. Careful and correct use of terms and definitionscan go far in improving our students’ conceptualunderstanding and problem-solving ability. In thenext article in this series, we will discuss a global approachto energy that can be used to address any energyproblem.6. As a textbook author myself, I do not specifically identifyproblematic statements in other authors’ textbooksin this series of articles. I do not want this series to appearas a marketing tool, but rather as a professionalcommunication that offers a set of suggestions for improvingthe teaching of energy to our students. I presentitems from several textbooks in general terms andnot as direct quotes.7. J.W. Jewett, “Energy and the confused student IV: Aglobal approach to energy,” Phys. Teach., to be publishedin April 2008.8. R. Baierlein, “Does nature convert mass into energy?”Am. J. Phys. 75, 320–325 (April 2007).PACS codes: 01.40.gb, 45.00.00John W. Jewett Jr. is professor emeritus at CaliforniaState Polytechnic University. He has authored The Worldof Physics; Mysteries, Magic, and Myth and co-authoredPhysics for Scientists and Engineers, seventh edition, andPrinciples of Physics, fourth edition. He won the AAPTExcellence in Undergraduate Physics Teaching Award in1998; jwjewett@csupomona.eduReferences1. J.W. Jewett, “Energy and the confused student II: Systems,”Phys. Teach. 46, 81–86 (Feb. 2008).2. This statement is made under the assumption that weignore internal structure of the object. Objects withinternal structure can possess potential energy. Forexample, a spring can possess elastic potential energyand a can of gasoline can possess chemical potentialenergy. These types of energy are associated with forcesbetween components of the structure of the object,however, not with forces between the object and otherobjects.3. R.H. Romer, “Heat is not a noun,” Am. J. Phys. 69,107–109 (Feb. 2001).4. R.P. Bauman, “Physics that textbook writers usually getwrong: II. Heat and energy,” Phys. Teach. 30, 353–356(Sept. 1992).5. G.M. Barrow, “Thermodynamics should be built onenergy—Not on heat and work,” J. Chem. Educ. 65(2),122–125 (Feb. 1988).The Physics Teacher ◆ Vol. 46, March 2008 153