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Physics teaching What contribution can be expected from physics education research?. Laurence Viennot LSDP, University Denis Diderot (Paris7) [email protected]  Attracting students towards physics : an urgent need.

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Physics teaching

What contribution can be expected from physics education research?

Laurence Viennot

LSDP, University Denis Diderot (Paris7)

[email protected]


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Attractingstudentstowardsphysics: an urgent need


Attracting students towards physics an irrecductible alternative l.jpg

Attracting students towards physics: an irrecductible alternative?

The nature of science:distorted?

Formalism: a stress to keep hidden?

It is theory that feeds and inspire creativity A. Fert 08

What about the value of the internal consistency, conciseness , and predictive power of physical theories?

What about the pleasure of reasoning?


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Suggestions for today …

Concerns of physics education research

(among others)

+ a few questions

+a concern for coherence

+ a « good method » ?

+ …

+ a concern for coherence

and conceptual links

Exciting topics

Small experiments

Ordinary topics

Mind rituals!


Exciting topics what do the students learn l.jpg

Exciting topicsWhat do the students learn?


The merits of new topics l.jpg

The merits of new topics

  • « True » physics, therefore (?) good physics

  • Prestige of cutting edge topics

  • View of science as evolutive


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  • Make new topics accessible to every kind of students? (LV GIREP-EPEC, Opatija 2007)

  • Make new topics accessible to everybody ? (LV ICPE-Marrakech 2007)


Appeal of new topics l.jpg

Appeal of « new »topics

Durban (ICPE 2004) « What physics should we teach ? »

  • Quantum gravity for undergraduates? R. de Mello Koch

  • A unit on (...) determinism and chaos for introductory physics students P. Laws

  • Illustrating quantum entanglement in an elementary context G. Roston et al.

  • Quantum mechanics for everyone: can it be done with technology?

    D. Zollman

An example:


Just an example l.jpg

  • A unit on (...) determinism and chaos for introductory physics studentLaws 04

Just an example…

Iterative spreadsheet modeling

I= mR2 + 1/2( MR2 )

 net =  grav +  damping +  springs + driver .


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Instructors expected them to be surprised that the state of a chaotic system is unpredictable when the torques acting on it are known.

…, we found that the Chaos Unit is both vexing and exciting to our students.

What did they learn?

Instead,studentsoftencommentedthatLaplaciandeterminismis not feasiblebecause of quantum effects.


Teaching exciting topics mission impossible l.jpg

Teaching « exciting » topics: mission impossible?

Certainly not, but a need for thorough reflexion, careful selection of goals and strategiesin order to

- provide students with some tools for reasoning

in order to

  • help them go further than being «both vexed and excited » ,

    …knowing their tendencies and needs


There are some good examples l.jpg

There ARE some good examples

  • For students:

    • Laws 04, Advancing physics (2000; Ogborn & coll.: Imaging), …

  • Public understanding of science:

    - Aspect 2000, …

    More details in Appendix, if some time is left


Small experiments what could they learn l.jpg

Small experimentsWhat could they learn?


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A ritual small experiment

water

cardboard

A recent workshop on physics education

The experiment of the glass filled with water + cardboard and turned upside down

The proposed explanation:

Cardboard will support water.

If turned around, the cardboard feels atmospheric pressure from below,

put into orbit?

cardboard

but only hydrostatic pressure of say, 10cm of liquid, i.e. 1/100 of atmospheric pressure from above


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Pressure forces exerted by water:a matter of weight of water (only)?

« What is pressing on the balloon that is immersed in the water?… water obviously.

When I pushed it into water, it felt

the pressure of water.

but also the air that is pressing on water

z

p= p0+gz

atmospheric pressure and

Marie Curie /I. Chavannes 1907


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Using simple experiments: more profitably?

- providing students with some tools for reasoning

 …

…knowing common tendencies and needs

  • « evidence », a notion to analyse carefully:

    • … avoiding to be misleading ?


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Method: a large consensus

Students should be active

Taking into account students’ common ideas

An experimental setting

Making and justifying some predictions

Well specified questions about the situation

Debates

Searching for a rational explanation


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Glass on Hand

W on G

A on G

Weight glass negl.

Glass

Hand on G

Water

C on W

G on W

E on W

Weight cardboard negl.

Cardboard

A on C

W on C

A: the atmosphere

G: glass

W: water

E: the Earth

The Earth

W on E


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G+W+C on Hand

Or much simpler…

A on G+W+C

Hand on G+W+C

Weight glass negl.

Glass

+Water

E on W+G+C

+Cardboard

A on C+W+G

Weight cardboard negl.

The Earth

W+G+C on E


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Hand

on G+W+C

A different spotlighting

Earth

on G+W+C


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Method: a large consensus…

…compatible with a wide range of strategies

Students should be active

Taking into account students’ common ideas

An experimental setting

Well specified questions about the situation

Making andjustifying some predictions

Searching for a rational explanation

Some debates


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Colour phenomenaChauvet 1994

  • White light

Wavelengths

…perceived responses to the received light

« third of a spectrum »


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absorbs

absorbs

absorbs

absorbs

absorbs

  • Pigments absorb a part of the received light and diffuse the remaining light.

A pigment

Red light Green light Blue light

Lum. Rouge Lum. Verte Lum. bleu

absorbs


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absorbs

A classic question…

  • Lit by red light, what colour will the letter V appear?

A rule: a green pigment

  • « Correct » answer: « the letter V appears black »

  • Common idea: red + green = brown (mixing paints)

  • Observed colour: brown!

(the room is not completely dark+ filter)

A common idea is reinforced


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Changing the questionChauvet 94

  • Lit by red light, is the letter V visible?

absorbs

nearly all…

  • Expected answer; «  the letter V is hardly visible , because the green pigment absorbs nearly all the light»

Which remains true in a real situation


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From a difficulty that is both technical and conceptual…

…to a stress on the absorption of light,renouncing the « all or nothing » approachand even …the colour!

A green pigment

absorbs

nearly all:


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…a stress on the absorption of light,renouncing the « all or nothing *» approachand even …the colour!

Very relevant from the standpoint of physics

Opens many opportunities to conduct experiments in a real situation and even…in the open air!

* Le matériau le plus noir: 0,045%

D.L., Sciences et Avenir March 2008, p23,


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Method: a large consensus…

…compatible with a wide range of strategies

Students should be active

Taking into account common ideas

A particular spotlighting of the content

Experimental

setting

Making and justifying predictions

Questions well specified

…aiming at conceptuals links

much more compatible with everyday life

debates

Searching for a rational explanation…


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Ordinary topics and the value of coherence


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Physics as an internally consistent and unifying description: an attractive idea?

If yes, then it is worth considering

the risks of inconsistency

some possible ways of showing the limited but great power of physics

An example with a very ordinary topic …


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A hot air balloon

A typical exercise:

  • A hot air balloon …a total mass of…

  • Whatever the temperature of the air in the balloon, its pressure will be the same as the surrounding air. (……….)

  • …Show that to achieve the lift off…must be heated to about ….° C.

pO

pO

pO

pO


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Archimedes upthrust : a matter of weights

Fbasket+… + gMair-inside = gM air-outside-sameV

Tin

Tout

Mair-inside = rair-inside V

Mair-outside-sameV = rair-outside V

pin = pout= p0

r = Mmol p0/RT

An example among MANY others: Giancoli,

ex. 37: Physics (6th ed). Prentice Hall

F


An example among many others giancoli physics 6th ed prentice hall l.jpg

Comm: G. Planinsic, 08/08

An example among MANY others: Giancoli, Physics (6th ed). Prentice Hall

  • 37.(II) A hot-air balloon achieves its buoyant lift by heating the air inside the balloon, which makes it less dense than the air outside. Suppose the volume of a balloon is and the required lift is 2700 N (rough estimate of the weight of the equipment and passenger). Calculate the temperature of the air inside the balloon which will produce the required lift. Assume that the outside air temperature is 0°C and that air is an ideal gas under these conditions. What factors limit the maximum altitude attainable by this method for a given load? (Neglect variables like wind.)

  • Solution (can be found in “Instructor Resource Center” CD-ROM, Prentice Hall, 2005) :

  • (…) The gas inside and outside the balloon is air, and so M is the same for inside and outside. Also, since the balloon is open to the atmosphere, the pressure in the balloon is the same as the pressure outside the balloon. (…)


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But…

Serious consequences

pO

pO

pO

« Local » ignores « global » and vice versa...

pO

g

Archimedes, where are you?


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Dpin= -ringDh

Dpout= -routgDh

p

rin< rout

Local

OK

Top Dh

Global and local reconciled

Global

Archimedes OK

pin > pout

Dh

pin = pout

pin> pout

Aperture

P

Viennot 04


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pO

pO

pO

pO

Thank you, you have made me think

Students’ reactions

  • No spontaneous detection

    (1st year: 15 interviews* + degree: N=32*+16**) (same for 76*+29 T-Teachers)

  • Guided analysis(1st year: 15 interviews*, degree: 21*+16**)

    -accessible ,

    -takes time but worth it

    -raised pleasure

Viennot 04*, 06*

Mathé Viennot 07**

A student: using critical sense: needs to be taught


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Thinking further?


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z+Dz

z

The weight of a gas… only one molecule

A particule

moving vertically in a motionless box,

elastic collisions on the walls

The mean force (in time) exerted by this particule on the box equals the weight of the particule 

True or false ?


An elastic collision l.jpg

An elastic collision …

A molecule (m) hits a wall perpendicularly with a velocity v et leaves this wall with velocity -v.

  • Change in linear momentum of the particule:

    Dp= -2mv

v


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v = (v+ D v) u

u

v (-u)

Change in linear momentum of the particule at the top of the box

Dptop= -2m (v + D v) u

D v<0

Change in linear momentum of the particule at the bottom of the box

Dpbottom= 2mv u

Change …during a « cycle » due to the box (up and down, two collisions) Dpparticule,cycle = -2mDv u


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Change …during a « cycle »(up and down)due to(two collisions with)the box

Dpparticule, cycle= -2mDv u

v = (v+ D v) u

u

v (-u)

Free fallDv = -gDtu

Mean force exerted on the particule by the box

during a cycle(2 Dt where Dt is the duration of free fall)

fmean force box-on-particule = Dp/2Dt

f mean force box-on-particule= mg u


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Third law

v = (v+ D v) u

f mean force box-on-particule= mg u

Therefore

v (-u)

f mean force particule-on-box = -mg u

The mean force exerted by the particule on the box is equal to its weight


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It had to be so

The mean position (in time) of the centre of mass of the particule during a cycle is the same for all the cycles

A Newtonian balance of forces :

f mean force box-on-particule+ ( -mg) u = 0

U

f mean force box-on-particule= mg u


Back to the atmosphere l.jpg

z

Back to the atmosphere …

  • This reasoning is valid no matter what the value of v.

  • It applies equally well to the vertical component of any non-vertical particular velocity.

  • The collisions between particles keep the linear momentum constant. The fact that they can intervene during the period considered does not change the mean force exerted in time by the molecules on the sides or the bottom of the box.


Links between l.jpg

z

z+Dz

z

Links between

An inhomogeneous slice

statics et dynamics

individual et collective

« it has to be so… » and «because»


Slide46 l.jpg

z+Dz

z

A few reactions


Students reactions 3 rd year univ n 13 l.jpg

Students’ reactions(3rd year univ., N= 13)

First question about a column of atmosphere:Yes 13/13

Then, question about a unique molecule: Yes 1/13


Destabilised trainee teachers first professional year n 19 sec 20 univ 39 l.jpg

z

z+dz

z

Destabilised trainee teachers(first professional year, N=19(sec.)+ 20 (univ.) = 39)

YN?

Is it true that …

The mean force exerted by the particle on the box is equal to its weight?

91812

The molecules, via collisions, exert the same force on the ground as if all the molecules of the column above were pile up, motionless, on the ground .

817 14

A slice of atmosphere … , the force df exerted on it by the air around ... and its weight dP are such that dP + df =0 , with dP=-g(z)dzdS u

20910

The weight of a column of atmosphere equals the force exerted on the ground by this column

2289


Students and tt reactions 3 rd year univ n 13 trainee univ teachers n 20 l.jpg

z+Dz

z

Students’ and TT’ reactions (3rd year univ., N= 13; trainee univ. teachers, N=20)

  • Guided analysis (in group, 20mn)

    -requires an effort, but accessible ,

    -worth the time it takes

    -raised pleasure

    - never thought before

- I like thinking about things that I never thought about before. (St. 3rd year)


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Students: more details


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An experienced teacher, interview

-P1It comes down to saying … transmitting the weight, uhm, by the bottom of the box or moving all around the box and exerting actions, pressing forces,… it comes to the same thing. Why does it come down to the same thing… uhm…????

(After explanation)

-P1 Oh yes, it’s because usually, when we study a gas, we neglect weight… we do not do it in a gravitational field …

…We have shown in that box there why the pressure was greater than there, we have shown it with g.


From the gas in a horizontal test tube to an atmosphere l.jpg

z+Dz

z

From the gas in a horizontal test tube to an atmosphere

From the hot air balloon to the single molecule

From macro-global

and macro-local

to nanoscopic

A continuity of mutually consistent viewpoints,

in the frame of Newtonian mechanics


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Ordinary topics, but less common questions…


Slide54 l.jpg

…a stress on coherence, and on links.

Two lines of action

-Many situations, a unique formalism

-A unique situation, different approaches


Many situations a unique formalism l.jpg

X

t

Many situations, a unique formalism …

  • The harmonic oscillator (60s)

  • √N, Poisson, exp-t/t: radioactive decay etc

    See Advancing Physics IoP (UK, 2000- Ogborn, in particular: Imaging++) , Grade 12 in France (2000)

  • Boltzmann factor, Change and Chance (Black,Ogborn, 70s),… Advancing Physics A2 (2001)

  • And also d=vt(Viennot/Leroy: delayed signals GIREP sem.2004)


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pO

pO

pO

pO

z+Dz

z

z

z+dz

z

but also

…different viewpoints for a given situation

See also

macro-micro (Härtel 93; Chabay-Scherwood 95, ..)

macro-meso Borghi et al. 96, Viennot 03, Besson Viennot 04


Spotlighting of the taught content precisely argued l.jpg

Physics education research: what can be expected …

Spotlighting of the taught content: precisely argued

After preliminary studies

(the content itself, history of science, students’ ideas) …

Ordinarytopics and classicexperimentsrevisited,

In particular, design of non ritualexperiments


How to teach friction experiments and models besson et al ajp 2007 75 12 1106 1113 l.jpg

How to teach friction: Experiments and modelsBesson et al. AJP 2007 75 12 1106-1113

One more example: the concept of dissipation


Slide59 l.jpg

Physics education research: what can be expected …

New topics: sameapproach

After preliminary studies

(the content itself, history of science, students’ ideas) …

Spotlighting of the taught content: preciselyargued

(…)

Stress on links


In general terms students declare their appreciation l.jpg

In general terms, students declare their appreciation …

Limited inquiry (LV)


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Reasons for satisfaction: students’ ranking(1: very high)

29 3rd year univ-students


Final comments l.jpg

Finalcomments


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pO

pO

pO

pO

without a strong exigence of consistency,

dislocated physics a near certainty

Strong concern for consistency and links

- awareness that finding answers to classic exercises is not enough

means

- thorough analysis of « details » relating to the physics content

- distance with respect to rituals

A cost in time and effort towards abstraction


Slide64 l.jpg

pO

pO

pO

pO

pO

pO

pO

pO

Univ. 1st

- It’s worth it, of course

-…provided we are taught how to do it

- Critical sense: it’s the most important thing, in my life.

- Sure, explanations, you shouldn’t give them thoughtlessly, you made me think, me, even if it’s difficult, it’s fine to think…We learn much more…I have learnt a lot.

- Thank you you have made me think

  • Why is it the first time someone tells me this?

  • Have you got anything else like that…

  • A topic which would at first glance be unattractive to me if I didn’t have to work on it. 

  • As it began with something that wasn’t obvious for me, […] the satisfaction is even greater because of all the difficulties I succeed in overcoming.

Grade 10

Univ. 3rd

Mediators-to-be


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pO

pO

pO

pO

without a strong exigence of consistency,

dislocated physics a near certainty

Strong concern for consistency and links

Intellectual satisfaction

A linkage worth exploring further


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  • « It’s worth it…

…provided we are taught how to do it »

If teachers agree to try ….

« Good for us,not for them »


Inciting teachers to try what can we do l.jpg

Inciting teachers to try…what can we do?


The conditions for teachers to hear l.jpg

Thank you, you have made me think

X

pO

pO

pO

pO

z+Dz

z

t

The conditions for teachers to hear…

……

commonly thought of as limited to non-classical activities with « relevant » , « exciting », …topics ?

Suggestion: consider it possible and necessary to

raise intellectual satisfaction, with ordinary topics as well

….


Some references l.jpg

X

pO

pO

z+Dz

z

pO

pO

t

Some references

  • VIENNOT L. 2003 Teaching physics Kluwer

  • BESSON, U. & VIENNOT L. 2004. Using models at mesoscopic scale in teaching physics: two experimental interventions on solid friction and fluid statics, IJSE, 26 (9), pp1083-1110

  • CHAUVET, F. 1996. Teaching Colour : Designing and Evaluation of a Sequence, European Journal of Teacher Education, 19, (2), pp. 119-134

  • VIENNOT L. 2004, ICPE meeting, Delhi

  • VIENNOT L. 2006.Teaching rituals and students' intellectual satisfaction, Phys. Educ. 41 pp. 400-408. http://stacks.iop.org/0031-9120/41/400.

  • MATHE, S. and VIENNOT, L. 2007, The concern for coherence among future science mediators, ESERA meeting Malmö.

  • LAWS, P. 2005, A unit on (...) determinism and chaos for introductory physics students, In What physics should we teach? Grayson, D.J. (Durban: Univ. of South Africa Press), p 198

  • VIENNOT L. & LEROY J.L. 2004. Doppler and Römer: what do they have in common? Phys. Educ., vol. 39, issue 3, pages 273 - 280.

  • VIENNOT, L. Le poids des mots, le choc des molécules. Bull. de l’UDPPC, To be published.

[email protected]


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