Welcome to the 2007 VUW Scholarship Physics Day

1. VICTORIA UNIVERSITY OF WELLINGTON • Te Whare Wananga o te Upoko o te Ika a Maui Welcome to the 2007 VUW Scholarship Physics Day Eclipsed in significanceonly by the shame of Trevor

2. 2 What’s the physics of this? Newton 3 If the caravan pulls back on the car as hard as the car pulls forward on the caravan, how can either of them move?

3. 3 What’s the physics of this? Newton 3 If the caravan pulls back on the car as hard as the car pulls forward on the caravan, how can either of them move?

4. Driving What forces act on the car?

5. Driving What forces act on the car? Common view: Normal support force Engine force Friction Weight

6. Driving What forces act on the car? Better view: Normal force of road on car Slipping friction Gripping friction of road on tyre Grav force of Earth on car • Tyre exerts backward grip friction force on road • evidence?

7. Driving What forces act on the car? Gravel spray  tyres push backwards on road  road pushes forward on tyres  gripping friction - bottom of rolling wheel does not move relative to road. (but gripping and slipping friction for a skidding wheel.)

8. Driving What forces act on the car?

9. Scholarship Physics Performance Standard p3 Format of the 2007 assessmentp5 Assessment Specificationsp6 Recent topic Coveragep7 Scholarship Physics 2005 p8 Scholarship Physics 2006 p22 Practice Questions p36 Practical Work p52 9

10. Being Physically Literate The things we encounter are usually tangible in nature but for the physics to be fully understood we have to move to the conceptual dimension where the behaviour of the world is interpreted in terms of key ideas and models. This can then be recorded and communicated in some representational language. 10

11. Being Physically Literate Understanding in physics is promoted and displayedwhen we describe and explain physical phenomenathrough the following dimensions: • tangible what can be seen and measured • conceptual the ideas, relationships, patterns and models • representational words, symbols, formulae, equations, graphs, diagrams, • calculations. 11

12. tangible conceptual representational Being Physically Literate To be physically literate you need to be able to work at each of these three levels and make connections between the levels in any discussion involving physical principles. Tangible observations of physical events and changes; measurements 12

13. tangible conceptual representational Being Physically Literate To be physically literate you need to be able to work at each of these three levels and make connections between the levels in any discussion involving physical principles. Conceptual thinking about key ideas, relationships, procedures and models needed to describe and explain what’s happening. “What’s the physics of it?” 13

14. tangible conceptual representational Being Physically Literate To be physically literate you need to be able to work at each of these three levels and make connections between the levels in any discussion involving physical principles. Representational using words, sentences, paragraphs, symbols, formulae, equations, graphs, diagrams, algebra and arithmetic as appropriate to convey your views with brevity, fullness and richness. 14

15. Scholarship Physics Standard p3 PD3 The student will: demonstrate explanations, analyses and problem solutions that consistently reflect exceptionally clear thinking together with depth and breadth of conceptual understanding. give concise explanations or analyses in terms of phenomena, concepts, principles and/or relationships that show clear understanding. abstract the relevant concepts and/or principles from physical situations and integrate these in the solution of complex problems. 15

16. Scholarship Physics Standard p3 PD2 The student will: demonstrate explanations, analyses and problem solutions that consistently reflect exceptionally clear thinking together with depth and breadth of conceptual understanding. give concise explanations or analyses in terms of phenomena, concepts, principles and/or relationships that show clear understanding. abstract the relevant concepts and/or principles from physical situations and integrate these in the solution of complex problems. 16

17. Scholarship Physics Standard p3 PD1 Outstanding Performance The student will: demonstrate explanations, analyses and problem solutions that consistently reflect exceptionally clear thinking together with depth and breadth of conceptual understanding. give concise explanations or analyses in terms of phenomena, concepts, principles and/or relationships that show clear understanding. abstract the relevant concepts and/or principles from physical situations and integrate these in the solution of complex problems. 17

18. Assessment Specification p6 • Format • 6 questions, short and long. • time indication • each question 8 marks  total 48 • may range across L3 AS • bring calculator and ruler • all necessary formulae, constants and data provided 18

19. Assessment Specification p6 • What you need to do: • All working should be shown in calculations. • Numerical answers should be rounded to an appropriate number of significant figures. • Correct units must be included. • Explanations and calculations are expected to be well set out and concise. 19

20. Assessment Specification p6 • Content/Context Details • L1 and 2 content knowledge may be needed. • Questions set within range of contexts - maybe unfamiliar. • Some “extended discussion” needed  writing skills. • Practical context  sources of error; • reliability of data; • validity of conclusions. 20

21. Scholarship Marking • Questions marked on 9-point scale. • You get 0 to 8. • Mark criteria for 2007 7-8 outstanding performance 5-6 scholarship performance 3-4 demonstrates understanding 1-2 meagre understanding relevant to the topic 21

22. The Chances • Number of Scholarships awarded is roughly 2 - 3% of the Level 3 physics cohort. • Level 3 physics cohort ≈ 6000 •  about 150  30 awards • About 1 in 6 sit schol; about 1000 • On the day, you have to be in the top 200. 22

23. Past results: a reality check Scholarship Physics 2005 • The average mark was below 17 out of 54. • Fewer than 1 in 10 candidates gained marks over 30. • Only 18 candidates gained more than 40.

24. Scholarship Candidate Profile The best performing physics candidates most commonly demonstrate the following skills and/or knowledge: • Ability to interpret an unfamiliar situation in context. • Significant physical insight across a wide variety of situations. • Ability to provide full but concise explanations. • Coherent and structured mathematical approaches to calculations. • Depth and breadth of conceptual understanding. • Understanding of mechanics and how to apply Newton’s laws correctly. • A good understanding of the practical implications of their answers and were able to determine if their answers made sense. • Recognition that scholarship calls for more than a superficial response. 24

25. Some comments from the examiner … candidates seemed to write large amounts when it may have been better for them to sit and think about the question first, and note that if their calculations were longer than a few lines then they should stop and see if they could find an easier method. Perhaps candidates need to be taught how to explore ideas before committing to one in exam situations. It seems that many candidates need to learn how to express themselves with clear thinking instead of the “shot-gun” approach to problem solving. It might be better for candidates to write bullet points at the start of the problem to help organise their thoughts before writing equations or explanations.

26. Recent Topic Coverage p7 3.3 Waves 2004 2005 2006 • Doppler blood flow • Bragg interference • electron diffraction • Lloyd’s mirror interference

27. Recent Topic Coverage p7 3.4 Mechanics 2004 2005 2006 • hammer throw rotation • angular momentum • CM orbit • planet spin disintegration, grav force, UCM • tethered orbit tension • momentum • phugoid oscillations • SUV stability, force/torque equilibrium • barge momentum forces • rope/pulley force diagram • geosynchronous satellite • force, terminal velocity, power

28. Recent Topic Coverage p7 3.5 Atoms & Nuclei 2004 2005 2006 • radioactive decay energy • binding energy

29. Recent Topic Coverage p7 3.6 Electromagnetism 2004 2005 2006 • RCL circuit • electric motor, back emf • Maglev train, magnetic fields & forces • DC circuits series/parallel • RC network • capacitors in parallel, dielectric, square pulse in RC circuit • RCL resonance • Faraday’s law.

30. 2004 Examiner’s Report • Candidates struggled with • applications of Newton’s Laws. • applying the Doppler effect in a less familiar context. • the conditions for interference and applications of interference and diffraction. • EM induction. 30

31. 2005 Examiner’s Report p8 Most candidates showed good understanding of: • simple momentum descriptions • the photoelectric effect • simple harmonic motion • the Doppler Effect. Most candidates had difficulty with: • applications of Newton’s laws including force vector resolution • conservation of angular momentum • simple DC circuit analysis, including capacitors in series. 31

32. 2006 Examiner’s Report p22 • Most candidates showed good understanding of: • the concept of binding energy and Einstein’s equation • gravitation in relation to geosynchronous satellites • constructive and destructive interference • RLC circuit theory. • Many candidates had difficulty with: • the relationship between energy and potential difference • applications of Newton’s laws • the simple pendulum, especially in relation to the measurement of the length of the pendulum • the necessary requirements for a geosynchronous satellite • applying the ideas of interference • applying Faraday’s law. 32

33. How to answer questions? • read the question, eg, Q2 p37, and read it again!

34. How to answer questions? • read the question, eg, Q2 p37, and read it again! • what’s going on? what’s the physics of it? • imagine the situation unfolding frame by frame, stage by stage • capacitor discharge • current pulse • magnetic field interaction • kicks rod up • initial KE to GPE

35. How to answer questions? • read the question, eg, Q2 p37, and read it again! • what’s going on? what’s the physics of it? • imagine the situation unfolding frame by frame, stage by stage • identify and list the general topic area(s) • capacitor discharge • current pulse • magnetic field interaction • kicks rod up • initial KE to GPE capacitors magnetic forces on currents impulse, change of momentum KE / GPE

36. How to answer questions? • read the question, eg, Q2 p37, and read it again! • what’s going on? what’s the physics of it? • imagine the situation unfolding frame by frame, stage by stage • identify and list the general topic area(s) • look at the formula page • it reminds you of key ideas and connections • ...and might suggest an idea you didn’t think of at first • loop back - it’s not a linear process • it’s a creative process - composing a symphony of physics • capacitor discharge • current pulse • magnetic field interaction • kicks rod up • initial KE to GPE capacitors magnetic forces on currents impulse, change of momentum KE / GPE

37. Equations impulse, change of momentum capacitors KE / GPE magnetic forces on currents? whoops - no formula - that’s level 2 stuff - you’ll just have to remember F=BIL

38. How to answer questions? • a chess player looking several moves ahead • stepping stones • mapping a route through conceptual network from question to answer

39. Practice problems p36-50 • Long-answer questions chosen from old UE Schol papers (pre-1989) to focus on areas highlighted by examiners’ reports as needing attention. • NZEST questions ignored, since you can download exams and answers. • Old questions stylistically different from current format – but the physics is the same, • as is the level of difficulty. 39

40. Problem-solving sessions • Groups of 2 or 3. Work together. • Pick a question - there are 20 to choose from. • Argue • Discuss • Focus on conceptual understanding first. • Focus on planning and crafting “good” answers: • Invisible Friend Solutions at www.physics.school.nz 40

41. How to approach the questions • Read the question carefully • Pick a question - there are 20 to choose from. • Argue • Discuss • Focus on conceptual understanding first. • Focus on planning and crafting “good” answers: • Invisible Friend

42. 1 2 3 When switch is closed, bulb 2 will stay same brightness get brighter get dimmer, go out. Appetiser 1

43. Appetiser 2 The 40 W bulb and the 100 W bulb are connected in series to the battery. Which bulb will glow brighter? 40 W bulb 100 W bulb