Appendix 4. Excerpts from Official Instructions on the Curriculum For Grades 9 and 11 (Science Section)
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Laws for quantities at time t
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to distinguish between local and global actions. As long as it is the motion of the whole that is
being considered (in fact, the motion of its centre of mass), it is not necessary to discuss the
point of application. If, on the other hand, the rotation or deformation of the object are
considered, then the problem cannot be avoided.
(...)
1.3 The key idea in this paragraph is that the friction force between the ground and the
moving object is necessary to propulsion. This idea must be introduced through
experimentation.
(...)
Excerpts from official comments on the grade 11 curriculum
(Bulletin Officiel, 1992b)
1.3 Interactions between objects
Various simple situations are described in terms of interactions, stress being laid on the
importance of contact actions and friction phenomena: contact between a tyre and the road,
the action of the wind, upthrust, etc. At this point it can be explained, for example, that it is
really friction that makes motion on the ground possible. It must be pointed out that contact
actions are generally repulsive, but one might bring up the fact that contact can be violently
attractive, as it is in the case of two perfectly smooth surfaces in contact with one another, and
adhesion techniques can be mentioned. (...)
The principle of “reciprocal interactions” or the principle of action and reaction” is in fact
Newton’s third law. It constitutes a major conceptual difficulty. It is, for example, difficult to
admit that even if a man is not touching the ground, he is exerting upon the Earth a force of
the same magnitude as his weight; or that a body immersed in a liquid exerts upon it a force
that is the opposite to the upthrust. Nor is it easy to accept that when one pushes down on an
object, the force it exerts in return is the opposite of the force exerted upon it. Rigorous
schematisation aids in establishing a distinction between forces: the forces exerted on a given
object, which are considered when adding together the forces acting on that object (with a
view to applying the principle of inertia and the fundamental relationship of dynamics at a
later time), and the two forces involved in the interaction, which are exerted on two different
objects and are always opposite forces. (...)
Even though formalism is not introduced until grade 11, it is important to illustrate with
concrete examples or experiments the consequences of
on the motion of the centre of
mass. In particular one needs to start eradicating the fallacious but widespread notion that
v=0 at time t implies
and that
implies.
Moreover, the “Accompanying Documents” (1992, 1993) established by the Technical
Group (GTD) for Physics, that formulated the curriculum proposals and comments, propose
two versions of the schematisation procedures described above (fragmented diagrams) for
grades 9 and 11.
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Chapter 4
REFERENCES
Andersson, B. 1986. The experiential Gestalt of Causation: a common core to pupils’
preconceptions in science. European Journal of Science Education, 8 (2), pp 155-171.
Bulletin Officiel du Ministère de l'Education Nationale, 1993, n°93, Nouveaux programmes
de physique et chimie pour la classe de Troisième des collèges, pp 3721-3737.
Bulletin Officiel du Ministère de l'Education Nationale, 1992b. Nouveaux programmes de
physique et chimie pour les classes de Seconde, Première, et Terminale des lycèes,
Numéro hors série du 24-9-1992, Vol II, p 38.
Caldas, E. 1994. Le frottement solide sec: le frottement de glissement et de non glissement.
Etude des difficultés des étudiants et analyse de manuels.. Thesis. Université Paris 7.
Caldas, E.and Saltiel, E. 1995. Le frottement cinétique: analyse des raisonnements des
étudiants. Didaskalia, 6, pp 55-71.
Driver, R., Guesne, E. and Tiberghien, A. 1985. Some features of Children's Ideas and their
Implications for Teaching, in Driver, R., Guesne, E. et Tiberghien, A. (eds): Children's
Ideas in Science. Open University Press, Milton Keynes, pp 193-201.
Groupe Technique Disciplinaire de Physique 1993. Document d'accompagnement du
programme de Troisième. Ministère de L'Education Nationale, Paris.
Groupe Technique Disciplinaire de Physique 1992. Document d'accompagnement du
programme de Première. Ministère de L'Education Nationale, Paris.
Gutierrez, R. and Ogborn, J. 1992. A causal framework for analysing alternative conceptions,
International Journal of Science Education. 14 (2), pp 201-220.
McDermott, L.C. 1984. Revue critique de la recherche dans le domaine de la mécanique.
Recherche en Didactique: les actes du premier atelier international, La Londe les Maures,
1993. CNRS, Paris, pp. 137-182.
Maurines, L. 1986. Premières notions sur la propagation des signaux mécaniques: étude des
difficultés des étudiants. Thesis. Université Paris 7.
Maurines, L. 1993. Mécanique spontanée du son. Trema. IUFM de Montpellier, pp 77-91.
Maurines, L. and Saltiel, E. 1988a. Mécanique spontanée du signal. Bulletin de l'Union des
Physiciens, 707, pp 1023-1041.
Maurines, L. and Saltiel, E. 1988b. Questionnaires de travail sur la propagation d'un signal,
Université Paris 7 (diffusion LDPES)
Menigaux, J. 1986. Analyse des interactions en classe de troisième. .Bulletin de l'Union des
Physiciens, 683, pp 761-778.
Saltiel, E. and Viennot, L. 1983. Questionnaires pour comprendre, Université Paris 7
(diffusion LDPES).
Saltiel, E. and Viennot, L. 1985. What do we learn from similarities between historical ideas
and the spontaneous reasoning of students? The many faces of teaching and learning
mechanics. In Lijnse, P. ed.. GIREP/SVO/UNESCO, pp 199-214.
Séré, M.G. 1982. A propos de quelques expériences sur les gaz: étude des schèmes
mécaniques mis en oeuvre par les enfants de 11 13 ans, Revue Franỗaise de Pộdagogie,
60, pp 43-49.
Séré, M.G. 1985. Analyse des conceptions de l'état gazeux qu'ont les enfants de 11 à 13 ans,
en liaison avec la notion de pression, et propositions de stratégies pédagogiques pour en
faciliter l'évolution. Thesis (Doctoral d'état). Université Paris 6.
Laws for quantities at time t
Viennot, L. 1979. Le raisonnement spontané en dynamique élémentaire, Hermann, Paris.
Viennot, L. 1979 Spontaneous Reasoning in Elementary Dynamics, European Journal of
Science Education, 2, pp 206-221.
Viennot, L. 1982a. L'action est-elle bien égale (et opposée) à la réaction?, Bulletin de l'Union
des Physiciens, n° 640, pp 479-488.
Viennot, L. 1985. Mécanique et énergie pour débutants, Université Paris 7 (LDPES).
Viennot, L. 1989a. Bilans de forces et lois des actions réciproques. Bulletin de l'Union des
Physiciens. 716, pp 951-970.
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Chapter 5
Quasistatic or causal changes in systems
In association with Jean-Louis Closset and Sylvie Rozier
To draw out and highlight the basic elements of physics and “natural”
reasoning, our analysis has, up to now, centred on changes in relatively
simple objects. But the complexities of nature and the possibilities of physics
are greater than those we have described, even if we remain within the realm
of the “elementary”.
1.
THE ESSENTIAL: SYSTEMS THAT OBEY
SIMPLE LAWS
Complex groups of elements in mutual interaction – “systems” – can
often be described relatively simply by means of a few laws.
What simplifies description is the hypothesis that these elements
mutually inform one another very quickly, relative to the time it typically
takes for the whole group to change. It is often said, for brevity’s sake, that
with these systems one can “neglect internal propagation,” which means,
more precisely, that one can neglect its duration. But this is an
approximation – one that allows certain laws to “hold” despite, and during, a
change in the system. One might call them “quasilegal” evolutions of
systems.
Textbooks use the adjectives “quasistationary” (in connection with
electricity, for example) or “quasistatic” (in connection with
thermodynamics). But there is one field in which, most of the time, no one
remembers to mention these types of change: elementary mechanics. The
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Chapter 5
particles of a solid mutually inform one another very quickly when anything
occurs (if the reader will forgive this anthropomorphic image). It therefore
seems unnecessary to specify that “one can neglect internal propagation of
effects”. Nevertheless, the transfer of information sometimes takes an
amount of time that is not negligible relative to the time scale of
characteristic events: there can be waves in solids, too.
Box 1 illustrates some simple examples of quasistatic analyses taken
from the fields of mechanics and electricity.
The notes accompanying each example show that many quantities are
involved: situations of this sort are generally called multi-variable, or
multifunctional, problems. Here, complexity is reduced, but not eliminated.
Then there are the laws. Some describe, in a phenomenological fashion,
each of the parts (the “subsystems”) involved. Others express relationships
between subsystems – e.g., those expressing conservation, or a fundamental
law, such as the law of reciprocal actions.
The general practice is to make no mention of time. But the remarks in
chapter 4 apply even more strongly here. Many of the quantities involved are