Teaching Physics

stephanie_pegg once recalled a time when she was taken off some or other project and asked to help her boss’s child with some or other school assignment. Well, recently the opposite happened to me: I was taken off some or other project to help set a school assignment for physics. I didn’t quite get to grips with whether it was bursary equivalent or only sixth form.

My task was to prepare first-principals workings and notes for a single degree of freedom oscillator without damping. As you can imagine, this was pretty straightforward for me, as I am used to rather more complex problems of oscillators with damping and so on. Although we don’t usually actually get to grips with the governing equations directly, for various reasons.

Anyway, having produced the kind of working and notes that could probably have been ripped straight from most first-year physics text books, I asked for a copy of the actual assignment to have a look. And I was a bit annoyed, actually, at the problem they’d set their students.

The situation described in the frippery as being the physical situation to model was the motion of a traffic light on an extension out over the road. This is a pretty common sight, and I think the teacher must have latched on to it on that basis. There was then a bunch of more technical stuff asking the student to attach a weight to a steel ruler and do some experiments on the position of the weight and the resultant “natural” frequency. This was to approximate the back-and-forth motion of the lights themselves if struck a glancing blow by a passing truck. Their model was appropriately simple: but not remotely similar to the real-world application they were supposed to have in the background of their minds!

My main beef is that the problem is not a 1 dimensional problem (which the spring-with-mass that I was asked to produce calculations for is), nor even a 2 dimensional problem (which the model they built is.) It’s a 3-D problem. The period of vibration will depend on the torsional strength of the pole and the bending stiffness of the arm. You can only start to solve the problem they ask for if you seriously neglect a lot of relatively important factors (the most important of which is neglecting the torsional stiffness of the pole, considering it infinitely stiff.)

Any child presented this problem, or indeed, presented any “real world” problem really needs to just chuck out the whole context they’re given and simply look at the material they have been taught and try to find something that looks applicable. In real life, that’s a dangerous game to play. I’ve been involved in peer-reviewing several jobs where an older engineer has simply made a bunch of approximations to squash their problem into the right shape for a solution they’ve been using for 40 years, and frankly, those solutions were just not good enough. A first-principals approach and appreciation of the complexity of the situation would have served them far better, if they’d been up to it.

What, in other words, was this round of experimentation supposed to actually teach them? That you’ve already got the answer, provided you can deem anything complex to be irrelevant? Is that the mode of thinking we should encourage? When I am instructing the technicians in various matters, I always try to break down my solutions into simple-enough parts, but I always pay special attention to why I am neglecting whatever features are irrelevant. These poor kids would just have had to guess.

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10 Responses to Teaching Physics

  1. Have you read _Surely you’re joking, Mr Feynman!_ ?

    • mashugenah says:

      No; indeed I have never heard of it. Is that a recommendation?

      • Well, I recommend the book in general. In specific, Feynman describes one instance when he was reviewing school science books — you might sympathize with him. I have a (rather battered) copy you may borrow if you wish.

  2. xullrae says:

    Hmm….it’s going to be interesting seeing the NZ education system through Savannah’s eyes as she grows up. I can sympathise with the physics teacher – it’s very difficult to find real-world examples that are appropriate in their complexity for schoolkids. Most of my A level work used ‘real world’ examples with the caveat that ‘we are ignoring X because it makes the problem too difficult’. I spent the next four years or so looking at almost exactly the same real-world problems, but each time a new layer of reality/complexity would be added. I think that’s perfectly reasonable, as long as the student understands why it’s being done.

    • mashugenah says:

      I think the teacher over-thought things. A perfectly ordinary traffic light without a long-arm is exactly the problem the students were asked to model. And that is a common real-world problem that entry-level structural engineers would be asked to solve…

  3. eloieli says:

    My conclusion, having trained and worked as a teacher, was that secondary education is less about teaching the subject and more about teaching different methods of learning and analysis.

    My experience of University is pretty much the same. It’s about teaching, incrememntally how to think.

    Now I can’t speak for Physics or English. But as an IT teacher the system is designed so that at year 13 (7th form) students should be able to tackle a project given certain requirements. So, for example, the project might be to develop a flyer, a brochure and a website for a real world customer. They find someone who wants it done. They sit with that person, documenting their requirements. Then they go away and brain storm solutions, all within the “project management” (read specific NCEA achievement standards) methodology they have been taught.

    They are to use the specific design process they have been taught. In Technology teaching of this process, if it occurs according to the curriculum, starts at year 1. In NCEA the model is basically: in Year 11 walk them through it step by step, teaching as you go. In Year 12 let them walk through it with you there. In Year 13, they do it and you (the teacher) are an expert resource they can draw on.

    So, back to the year thirteen project. They go between their stakeholders, the teacher and the customer, and have to build the solution based on those relationships and constraints.

    This is remarkably like real life. If I had some of Natalya’s year 12 or 13 IT and Design students to work train up I’d get better and more thorough work out of them than I get from some developers and testers who have been in the game for years.

    But, and this is the key thing. They are still only teenagers. They are still learning the ropes of decision making, analysis, project management etc. They still get a lot of support.

    And, if they went onto study this stuff and uni it probably wouldn’t be until honours that they got their first change at real independence. Like you, I didn’t get that in Psych until honours.

    The best thing about Philosophy was that you started to get it right at the beginning ^_^

    You, as a practicing and experience engineer, need to dumb down to their level to see the learning from their level. It’s one of the hardest things skills a teacher has to learn, to pitch the material at the right level and present it in an understanding and interesting way.

    I am not really sure if any of that actually makes a point or not. But there you go. I don’t want to write the Test Plan I am working on.

  4. mattcowens says:

    It was surprisingly hard to get some students to work out that the purpose of an advertisement is to sell the product. I don’t think they were ‘over-thinking’ the problem; quite the opposite.

    Student: “It’s an ad for shoes.”
    Teacher: “Why was it made?”
    Student: “I dunno.”
    Teacher: “Who paid for it?”
    Student: “Shoe people.”
    Teacher: “Why?”
    Student: “I dunno. This is stupid. I’m failing anyway.”

    Tick-box assessment doesn’t have to drive tick-box teaching, but often it does. For some students, getting their head around the tick-boxes is a big achievement in and of itself 🙂

    An example of the language problem:

    An exam essay about a novel. The aim is to test whether a student understands specified aspects of the novel (like theme, characters, setting etc.). It also tests:

    – speed of writing
    – ability to handle exam pressure
    – ability to read, comprehend and respond to NCEA style questions
    – recall (especially important for quotes)

    It tests both what you know about the book, and how good you are at doing exams. Looking at that ad-hoc list, there does seem to be one item which could be eliminated, or at least made less of a barrier, to assessing the thing which the exam is supposed to be looking at.

    • mashugenah says:

      I don’t think they were ‘over-thinking’ the problem; quite the opposite.

      Depends on the student. I was a just-below-scholarship English student , and I often found the marks I lost were for just the lack of simple restatement as in your example. It’s a shoe advert, I struggle to see why I would re-state that in my answer.

      That was my problem answering the trepanation thing. “What is the message” Well, “don’t trepanate”… if you are smart enough to read my answer, you don’t actually need that answer from me: it’s in the source material.

      • mattcowens says:

        Yeah, this was a task for below-average students, so the example was blindingly obvious.

        I had students last year who did suffer from the ‘why should I restate the obvious?’ problem. They looked for a deeper meaning, or questioned the validity of ascribing a motive to an author you don’t know. In the end-of-year exams there’s a non-verbal clue for students which is quite handy:

        If there’s only space in the booklet for a short answer, the examiner wants you to give a simple answer.

        I tried to get those students to put aside their concerns about stating the obvious, start their answer with the basics, and build up from there.

  5. mattcowens says:

    Give the kids a bunch of key words, and in their response to your “question” they simply work through the list ticking them off.

    This is probably a good place to start. But it really can’t be where you end up.

    Agreed. To echo other-Matt’s comment, you aim to get a lot more complex and independent as you approach Y13. Not all students manage that, but that’s the aim. The example I gave was a slightly simplified practice text for Y11 (fifth form – 15yr olds) alternate class.

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