Attracting students towards physics A matter of topic?

1. Attracting students towards physics A matter of topic? Laurence Viennot LSDP, University Denis Diderot (Paris7)

2. Research on students’ motivation • A large part of this research domain is mainly focused on topics likely to raise interest in young people ex: ROSE Schreiner & Sjøberg, 2005 • A few studies also explore other aspects (type of activity, context) likely to attract students’ interest ex Häussler et al.,1998; Stark & Gray, 1999; Lavonen et al., 2005; Trumper, 2006

3. Searching for exciting topics • In recent school curricula or university syllabuses : a search for topics that are • relevant (physics in context), • exciting (« new », beautiful , makes you dream, incredible…) • preferably: both • Popularisation papers or events (ex: year 2005): - same concern But…

4. Attracting students towards physics: an irrecductible alternative? The nature of science:distorted? Formalism: a stress to keep hidden? What about the value of the internal consistency, conciseness , and predictive power of physical theories? What about the pleasure of reasoning?

5. What do we do with (reputedly) attractive topics? -How to make old topics (usefully) attractive? From the standpoint of: the value of the internal consistency, conciseness and predictive power of physical theories

6. Appeal of « new »topics An example: 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

7. « New » topics: with technology • Quantum mechanics for everyone: can it be done with technology?D. Zollman …for high school students and for non-science college students Getting round a discouraging formalism http://web.phys.ksu.edu/vqm/

8. … discrete states in quantum wells. The (…) program enables students to match wave fonctions visually at boundaries. They find that if they pick a random energy for a particle in a square well, the wave function does not fit* at both boundaries. *i.e.: they cannot obtain « smoothness » They get the functions matched up on one side, then try to meet the conditions on the other side. They can’t do it. Only for certain energies can they meet the boundary conditions on both sides.

9. To give a first idea of…, students in an active attitude, excited… A priori: undeniable positive outcomes, What did they learn?

10. Only for certain energies can they meet the boundary conditions for both sides… Our testing indicates that they are learning the material What does it mean to « learn the material »? Concepts and links between concepts? Given this simulation, what is their view of the generalisability of what they see? What is the kind of reasoning that students are expected to use, on the basis of their « learning »? (in the absence of a computer) Some non-obvious questions

11. A « new » topics: with (transparent) technology • A unit on (...) determinism and chaos for introductory physics studentsP. Laws

12. Priscilla Laws

13. Iterative spreadsheet modeling  net =  grav +  damping +  springs + driver . I= mR2 + 1/2( MR2 )

14. To give a first idea of…, students in an active attitude, … A priori: undeniable positive outcomes, What did they learn?

15. From the standpoint of: the value of the internal consistency, conciseness and predictive power of physical theories Finding a map for this jungle?

16. ... to understand, (…) …, that determinism is there… Several interrelated concepts … although« the system motion becomes chaotic when driven at certain frequencies. » Why? « Students are asked to observe the natural oscillation frequencies of the apparatus when it is configured in different ways. This helps them understand why the system motion becomes chaotic when driven at certain frequencies. »

17. What did they learn? Instructors expected them to be surprised that the state of a chaotic system is unpredictable when the torques acting on it are known. Instead, students often commented that Laplacian determinism is not feasible because of quantum effects. …, we found that the Chaos Unit is both vexing and exciting to our students.

18. Non-obvious questions… Beyond « showing » students that their predictions fail to describe what happens, how do we take into account students’ common ideas ?

19. Non-obvious questions… Beyond working with a particular device, and « seeing » …, do students grasp some • concepts, links between concepts, • understanding of the generalisibility, idea of a domain of validity • feeling of having an explanation (beyond a phenomenology) • tools available to reason about a new situation ? …not to be overlooked, whatever the approach: simulation, analytical, analogical…

20. A « new » topic with simple tools to reason A set of interrelated concepts Imaging Ogborn and coll. 00, Advancing physics (AS-UK) Pixels, resolution, logarithmic scale, information in imaging, image processing Replace each pixel by the mean of its value and those of its neighbours …median… « New » , « in context » ,. and enabling students to reason.

21. « New » topics: mission impossible? Certainly not, but a need for thorough reflexion, careful selection of goals and strategies…

22. The question is not so much to get round the formalism as to - provide students with some tools for reasoning in order to • help them go further than being «both vexed and excited ». A need to evaluate the innovative sequences  Komorek & Duit IJSE 04 From the standpoint of: the value of the internal consistency, conciseness and predictive power of physical theories

23. Ordinary topics and the value of internal consistency

24. 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 …

25. 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

26. Archimedes upthrust : a matter of weights Fbasket+… + gMair-inside = gM air-outside-sameV Tin Tout pin = pout= p0 Mair-inside = rair-inside V Mair-outside-sameV = rair-outside V r = Mmol p0/RT F

27. But… Serious consequences pO pO pO « Local » ignores « global » and vice versa... pO g Archimedes, where are you?

28. 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

29. 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 Teachers*) • Guided analysis(1st year: 15 interviews*, degree: 21*+15**) -accessible , -takes time but worth it -raised pleasure Viennot 04*, 06* Mathé Viennot 07** A student: using critical sense: needs to be taught

30. Thinking further?

31. 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 ?

32. 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

33. 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

34. 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

35. 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

36. 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

37. z z+Dz z Links between An inhomogeneous slice statics et dynamics individual et collective « it has to be so… » and «because»

38. z+Dz z A few reactions

39. z z+dz z Destabilised trainee teachers(first professional year, N=19) YN? Is it true that … The mean force exerted by the particle on the box is equal to its weight? 5104 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 . 59 5 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 838 The weight of a column of atmosphere equals the force exerted on the ground by this column 1153

40. Students’ reactions (3rd year univ., N= 13; trainee univ. teacher, N=9) z+Dz z • Guided analysis (in group, 20mn) -accessible , -worth the time it takes -raised pleasure - never thought before

41. Students’ reactions , more details(3rd year univ., N= 13) First question about a column of atmosphere:Yes 13/13 Then, question about a unique molecule: Yes 1/13 Then, the preceding analysis is presented: • Explains simply a fundamental question that is not very easy to explain simply to students intuitively. (4,4) - I like thinking about things that I never thought about before. (4,4) Students’ comments

42. Finally (without interval):

43. An experienced teacher, interview (Only one, « agitated », molecule in the box) -P1 It comes down to saying being at the botttom of the box and therefore… 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.

44. 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

45. Ordinary topics, but less common questions…

46. In general terms, students’ declare their appreciation … Limited inquiry

47. Reasons for satisfaction: students’ ranking(1: very high) 29 3rd year univ-students

48. …a stress on coherence, and on links. Two lines of action -Many situations, a unique formalism -A unique situation, different approaches

49. 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)

50. pO pO pO pO z+Dz z z z+dz z but also …different viewpoints for a given situation See also macro-meso: Besson Viennot 04