IB Physics is Too Hard

For several years, I have harboured the notion that IB Physics is too hard. I suspect I’m not the only one:

For a student, the difficulty of physics is perhaps easier to explain: the ways of constructing meaning are challenging, the models of knowledge demand careful study for mastery, and the assessments are notoriously hard to bluff your way through. For educators, however, these difficulties are part of the trade. Textbooks, lesson plans, and pedagogical approaches provide good ways for students to overcome these issues.

Even as an educator, however, IB physics still seems hard. Some people believe that the syllabus is too broad, encompassing too many topics like particle physics, wave interference, thermodynamics, and the greenhouse effect. Others point to the depth of understanding required to score well on the exams. However, I don’t think that either of these dimensions is sufficient to explain what is so hard about the syllabus.


I’ve added a third dimension to the “iceberg” of physics. Thickness is about the skills students need to acquire in order to do physics. To see this, let’s look at some examples.


Example 1: There’s a car on a hill, with lots of known properties.

  • Depth – what is the car’s velocity at the bottom of the hill? what is the efficiency of the car’s motion? if the car were to roll back up a similar hill, how far would it go?
  • Breadth – what would be the impact of a non-zero drag force? how does the calculation change if you consider the angular momentum of the wheels? at what rate is the car increasing the temperature of the hill?
  • Thickness – how do we know to use energy conservation? what does our model include? how can we understand the energy transformations within this model? how do we know if our answer is reasonable?

Screen Shot 2016-04-03 at 6.38.02 PM

Example 2: A past IB exam problem (above)

In this problem, students are expected to use the Rayleigh criterion to estimate resolution. It is a simple calculation that they have already done a few times, using a formula from the data booklet. This topic demonstrates both the breadth and depth (this is from a unit on single-slit interference) of the IB physics curriculum. It also demonstrates thickness: conceptually understanding what is going on here is very challenging. Although this appears on an exam, I suspect most IB physics students have just memorized how to use the formula.


Thickness in physics involves the skills, approaches, mindsets, and contextual knowledge that allows physicists to do physics. This includes things like critical thinking, building models, visualizing phenomena, drawing representative diagrams, working fluently with numbers, dimensional analysis, and using the right model at the right time.

IB Physics is hard because we neglect the thickness of physics, focusing on solving standard problems and preparing for tests instead of learning the skills of physics. And when students do well in this hard course, it isn’t because they mastered physics: it is because they did well on the test.

Let’s return to the tweet by @AfroRose_: “I remember when I was in IB physics, it was so hard. What’s crazy was in class I always got the answers right, but I couldn’t explain myself [emphasis added]”. Here is a student who studied hard and succeeded at IB physics, but never became competent with the skills involved in the discipline itself. For her, physics was deep, broad, and thin.

Over the past two years, I have tried to reconcile a deep, narrow, thick pedagogy (Modeling instruction) with a deep, broad, thin syllabus. There have been productive moments — the thickness is especially valuable in preparing students for their independent investigations — but any concession toward thick teaching comes at a cost in contact hours and, since the alternative is to prepare students directly for their exams, potentially a decrease in student grades.


How can IB Physics be more thick?

The AP and A-level boards have both done an admirable job in their past revision cycles of cutting down the amount of material students need to learn, that is, decreasing the breadth. The IB revision cycle sort-of-not-really did this, by reducing the number of optional topics, and shoehorning some extra particle physics into its place. A decrease in breadth is necessary because of the limited amount of time available for learning.

With a bit more time allowed for the development of skills with mechanics, for example, we could include system schemata, LOL diagrams, or graphical vector addition for forces. If we keep Feynman diagrams, we could have enough time to develop students’ understanding of them. With scaffolds like these, we could be confident that students will be better prepared to tackle unfamiliar, complex problems on exams. This could even allow for the use of open-ended problems. I think that would be pretty cool.

A change to a syllabus that seems to make it less hard will always be met with concern. I want to smart-up students, not dumb-down the curriculum. In any case, I wouldn’t be worried about blowback.


2 thoughts on “IB Physics is Too Hard

  1. Andy "SuperFly" Rundquist

    As my son is starting to take some AP courses in high school (so far bio and chem) I think about this a lot. I really like your descriptions of thickness, depth, breadth, etc. In Global Physics Department we often talk about the best experience a student could have. Sadly those conversations often come to a crashing halt when someone remembers that they have to teach AP (IB isn’t as common in those conversations, but I gather it would work similarly).

  2. kbf

    Thanks for sharing this Danny. More and more I find myself questioning the purpose of teaching IB Physics. For weeks, I have been studying the Relativity option to teach my students, and I can’t imagine how long it would take students to develop a deep understand of the topic, rather than just learn a few tricks to get the right answer. We all end up teaching, some of the curriculum, to the test. I remember 5 years ago a student of my (he got a 7 in the exam) came back to visit and told me “Mr. Feitosa, I don’t think I can remember 10% of what I learned in IB Physics” — this is just one year after graduating. All of this happen before I started adopting modeling practices in my classes, but time constrains still forces me to go back to old ways. Thanks again for posting.


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