<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>1870-3542</journal-id>
<journal-title><![CDATA[Revista mexicana de física E]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. mex. fís. E]]></abbrev-journal-title>
<issn>1870-3542</issn>
<publisher>
<publisher-name><![CDATA[Sociedad Mexicana de Física]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S1870-35422009000100004</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Students' difficulties with tension in massless strings. Part I]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Flores-García]]></surname>
<given-names><![CDATA[S.]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Alfaro-Avena]]></surname>
<given-names><![CDATA[L.L.]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Chávez-Pierce]]></surname>
<given-names><![CDATA[J.E.]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Estrada]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Barrón-López]]></surname>
<given-names><![CDATA[J.V.]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[González-Quezada]]></surname>
<given-names><![CDATA[M.D.]]></given-names>
</name>
<xref ref-type="aff" rid="A02"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Universidad Autónoma de Ciudad Juárez  ]]></institution>
<addr-line><![CDATA[Ciudad Juárez Chih.]]></addr-line>
</aff>
<aff id="A02">
<institution><![CDATA[,Instituto Tecnológico de Ciudad Juárez  ]]></institution>
<addr-line><![CDATA[Ciudad Juárez Chih.]]></addr-line>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>06</month>
<year>2009</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>06</month>
<year>2009</year>
</pub-date>
<volume>55</volume>
<numero>1</numero>
<fpage>21</fpage>
<lpage>33</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S1870-35422009000100004&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S1870-35422009000100004&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S1870-35422009000100004&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Many students enrolled in the introductory mechanics courses have learning difficulties related to the concept of force in the context of tension in massless strings. One of the potential causes could be a lack of functional understanding through a traditional instruction. In this article, we show a collection of this kind of students' difficulties at the New México State University, at the Arizona State University, and at the Independent university of Ciudad Juárez in México. These difficulties were collected during an investigation conducted not only in lab sessions but also in lecture sessions. The first part of the investigation is developed in the contexts of proximity and the length of strings.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Muchos estudiantes de los cursos introductorios de mecánica presentan serias dificultades para comprender el concepto de fuerza como vector en el contexto de la tensión en cuerdas de masa despreciable. Una de las posibles causas es la falta de entendimiento funcional desarrollado durante las clases fundamentadas en una enseñanza tradicional. En este artículo, presentamos una serie de este tipo de problemas de aprendizaje que tienen los alumnos de los cursos de física clásica y estática en la Universidad Estatal de Nuevo México, en la Universidad Estatal de Arizona y en la Universidad Autónoma de Ciudad Juárez. Estas dificultades de aprendizaje se obtienen durante una investigación conducida tanto en laboratorios como en el salón de clases. En la primera parte de la investigación se tratan los contextos de proximidad y longitud de las cuerdas.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Tension]]></kwd>
<kwd lng="en"><![CDATA[forces in strings]]></kwd>
<kwd lng="en"><![CDATA[learning difficulties]]></kwd>
<kwd lng="en"><![CDATA[force as a tension]]></kwd>
<kwd lng="es"><![CDATA[Tensión]]></kwd>
<kwd lng="es"><![CDATA[fuerzas en cuerdas]]></kwd>
<kwd lng="es"><![CDATA[dificultades de aprendizaje]]></kwd>
<kwd lng="es"><![CDATA[fuerza como una tensión]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ <p align="justify"><font face="verdana" size="4">Ense&ntilde;anza</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="center"><font face="verdana" size="4"><b>Students' difficulties with tension in massless strings. Part I.</b></font></p>     <p align="center"><font face="verdana" size="2">&nbsp;</font></p>     <p align="center"><font face="verdana" size="2"><b>S. Flores&#150;Garc&iacute;a&ordf;, L.L. Alfaro&#150;Avena&ordf;, J.E. Ch&aacute;vez&#150;Pierce&ordf;, J. Estrada&ordf;, J.V. Barr&oacute;n&#150;L&oacute;pez&ordf; and M.D. Gonz&aacute;lez&#150;Quezada<sup>b</sup></b></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><i><sup>1</sup> Universidad Aut&oacute;noma de Ciudad Ju&aacute;rez, Avenida del Charro 450 Nte. Col. Partido Romero 32310 Ciudad Ju&aacute;rez Chih.</i></font></p>     <p align="justify"><font face="verdana" size="2"><i><sup>2</sup> Instituto Tecnol&oacute;gico de Ciudad Ju&aacute;rez, Avenida Tecnol&oacute;gico 1340, Fracc. Crucero 32500 Ciudad Ju&aacute;rez Chih.</i></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2">Recibido el 27 de marzo de 2008    ]]></body>
<body><![CDATA[<br> Aceptado el 27 de enero de 2009</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>Abstract</b></font></p>     <p align="justify"><font face="verdana" size="2">Many students enrolled in the introductory mechanics courses have learning difficulties related to the concept of force in the context of tension in massless strings. One of the potential causes could be a lack of functional understanding through a traditional instruction. In this article, we show a collection of this kind of students' difficulties at the New M&eacute;xico State University, at the Arizona State University, and at the Independent university of Ciudad Ju&aacute;rez in M&eacute;xico. These difficulties were collected during an investigation conducted not only in lab sessions but also in lecture sessions. The first part of the investigation is developed in the contexts of proximity and the length of strings.</font></p>     <p align="justify"><font face="verdana" size="2"><b>Keywords:</b> Tension; forces in strings; learning difficulties; force as a tension.</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>Resumen</b></font></p>     <p align="justify"><font face="verdana" size="2">Muchos estudiantes de los cursos introductorios de mec&aacute;nica presentan serias dificultades para comprender el concepto de fuerza como vector en el contexto de la tensi&oacute;n en cuerdas de masa despreciable. Una de las posibles causas es la falta de entendimiento funcional desarrollado durante las clases fundamentadas en una ense&ntilde;anza tradicional. En este art&iacute;culo, presentamos una serie de este tipo de problemas de aprendizaje que tienen los alumnos de los cursos de f&iacute;sica cl&aacute;sica y est&aacute;tica en la Universidad Estatal de Nuevo M&eacute;xico, en la Universidad Estatal de Arizona y en la Universidad Aut&oacute;noma de Ciudad Ju&aacute;rez. Estas dificultades de aprendizaje se obtienen durante una investigaci&oacute;n conducida tanto en laboratorios como en el sal&oacute;n de clases. En la primera parte de la investigaci&oacute;n se tratan los contextos de proximidad y longitud de las cuerdas.</font></p>     <p align="justify"><font face="verdana" size="2"><b>Descriptores:</b> Tensi&oacute;n;    fuerzas en cuerdas; dificultades de aprendizaje; fuerza como una tensi&oacute;n.</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     ]]></body>
<body><![CDATA[<p align="justify"><font face="verdana" size="2">PACS: 01.40.d; 01.40.Fk; 01.49.Ha</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><a href="/pdf/rmfe/v55n1/v55n1a4.pdf" target="_blank">DESCARGAR ART&Iacute;CULO EN FORMATO PDF</a></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>References</b></font></p>     <!-- ref --><p align="justify"><font face="verdana" size="2">1. E.F. Redish, J.M. Saul and R.N. Steinberg, <i>Am. J. 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