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Abstract
The idea that liquids exert a force -called buoyancy force or up thrust- on objects immersed in them is part of a typical school science curriculum and is integral to explaining why some objects float. However, an explanation of how this force originates is often not provided at school level, and this may make its nature rather mysterious to students and give rise to difficulties in using the idea. In this article various kinds of explanation of buoyancy force available in the literature are explored, including the place of ARCHIMEDES' Principle. A way of simplifying fluid mechanics analysis of fluid pressure and pressing force is presented and suggested as a possible way of explaining buoyancy force at school level. Implications for teaching this area of physics are discussed.
Key Words: flotation; buoyancy force; fluid mechanics; fluid pressure.
Resumen
La idea que los liquidos ejercen unafuerza llamada fuerza de flotación sobre objetos sumergidos es parte del currícula de ciencia en la escuela y es esencial para explicar par qué flotan algunos objetos. Sin embargo, una explicación de cómo estafuerza se origina no es proveída a menudo en el ámbito de la escuela, y par esta razón su naturaleza puede ser misteriosa a los estudiantes y aumentar las dificultades al usar este concepto. En este articula son analizados varias tipos de explicación de lafiierza de flotabilidad disponible en la literatura, induyendo el principle de ARQUÍMEDES. Se presenta una manera de simplificar el análisis de la presión de fluidos y la fuerza de presión, sugerida como una manera posible de explicar lafuerza de flotación en el ámbito de la escuela. Las implicaciones para enseñar esta área de física son discutidas.
Palabras clave: flotación; fuerza de flotación; mecánica defluidos; presión de fluidos.
INTRODUCTION
On our initial teacher training courses in science, we include study of a phenomenon that continues to fascinate both children and adults and has an accepted place in the science curriculum: that of the floating and sinking of objects placed in water. We obviously want to include explanations of this and also to provoke student teachers to think through their own ideas. But what level of explanation is appropriate? KOLIOPOULOS et al (2004) make the useful point that floating is explained in terms...