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Appendix 4. Excerpts from Official Instructions on the Curriculum For Grades 9 and 11 (Science Section)

# 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

89

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.

(...)

(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

90

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

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.

91

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

93

94

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

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Appendix 4. Excerpts from Official Instructions on the Curriculum For Grades 9 and 11 (Science Section)

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