The Physics IA: What Do You Actually Need to Know for IB Physics?

The Physics IA is a single written report, up to 3,000 words, based on your own investigation into a physics question you design and test. It's marked internally by your teacher against five criteria worth 24 marks total, then externally moderated — worth 20% of your final grade at both SL and HL.

The IB caps the Physics IA at 3,000 words — that's a hard limit, not a target. I tell my students to aim for 2,200–2,600 words in the actual prose; the rest of your space should go on a clean data table, a graph, and your uncertainty calculations, which don't count toward the word limit if labelled as figures.

Your teacher marks your IA against the five official criteria (personal engagement, exploration, analysis, evaluation, communication) totalling 24 marks, then a sample from your school is externally moderated by the IB. The final mark converts to a percentage of your overall Physics grade — 20% at both SL and HL.

A good topic is one you can genuinely control and measure — not one that just sounds impressive. Pick something with a clear independent variable you can vary at least five times, a dependent variable you can measure precisely, and enough physics behind it to justify real analysis. Avoid anything requiring equipment your school doesn't have.

The IAs that score full marks share one thing: the student clearly owns the question and the data tells a complete, honest story — including where it falls apart. Uncertainty analysis is genuinely propagated through calculations (not just quoted once), and the evaluation names specific, fixable limitations rather than "human error" or "equipment was inaccurate."

A weak research question is descriptive — "How does temperature affect a bouncing ball?" A strong one is precise and measurable — "How does the drop height of a rubber ball (0.2–1.0 m) affect its coefficient of restitution when dropped onto a wooden surface?" Specificity in variables and range is what separates band 5-6 exploration marks from band 1-2.

Simulation-based IAs are allowed but score lower on personal engagement unless you justify why hands-on data collection wasn't feasible — genuine safety or access constraints, not convenience. Examiners moderating these look for evidence you understood the underlying model, not just that you changed sliders and recorded outputs.

The three mistakes I see every year: too few data points (fewer than 5 trials per variable), no error bars or uncertainty propagation on graphs, and a conclusion that just restates the results instead of comparing them to theory. Any one of these caps you well below a 6 on that criterion.

There's no fixed IB rule, but examiners consistently expect at least 5 values of your independent variable, each repeated 3 times, to allow meaningful averages and uncertainty ranges. Fewer than that and your analysis criterion mark drops — you simply can't show a reliable trend or calculate a sensible standard deviation.

Most schools schedule the Physics IA in the first half of Year 2 (or late Year 1 at some schools), giving 4-6 weeks including data collection, analysis and writing. Start topic selection at least two weeks before your first lab slot — the biggest time-waster is discovering in week two that your equipment can't measure what you need.

The Physics IA counts for 20% of the final IB Physics grade at both SL and HL — the same weighting across both levels. The remaining 80% comes from Paper 1, Paper 2 and Paper 3, so a weak IA can still be offset by strong exam performance, but it's worth taking seriously early rather than leaving it to catch up later.

No — the Physics IA is a one-shot internal assessment submitted once per student per session; it can't be resubmitted after final marking without exceptional circumstances (such as a documented IB-approved extenuating circumstance). This is exactly why getting the research question and data collection right early matters more than any exam revision session could fix later.

Beyond what their teacher provides, students benefit most from seeing worked examples of uncertainty calculations and sample high-scoring reports to understand what "good" actually looks like against the criteria. RevisionPrep's Physics Revision Notes and Topical Worksheets cover the maths skills (uncertainty propagation, graph linearisation) that underpin a strong IA, even though the IA topic itself is always student-chosen.