A-Level Physics 9702 Paper 3: Practical Design, Uncertainty and Graphs

Physics: the advanced practical paper

This paper marks experimental design and data handling: uncertainties, gradients and error analysis. The data you are given is never perfect, and the marks sit in how you handle the imperfection. This page sets out the scoring sentences, a 12-week timetable and the error log.

Paper 3 technique: name the instrument and its precision first, then the readings and the uncertainty, and only then the result. Percentage uncertainty = error / reading x 100%; the area factor (pi d^2 / 4) doubles the diameter uncertainty. Split a curve into a triangle and a trapezium instead of counting squares by eye.

Subject-specific weighting for this timetable: Weeks 1-3: uncertainty only. Write every reading as value plus or minus uncertainty, convert to a percentage, and say which measurement carries the largest percentage error, in numbers rather than by feel.
Weeks 4-6: graphs. Tabulate, plot, draw a line of best fit and take the gradient from two points on that line; then draw the steepest and shallowest acceptable lines for the limits.
Weeks 7-9: design. State what is measured, with which instrument, which variables are controlled and how many repeats; write only executable steps, never “ensure accuracy”.
Weeks 10-12: full papers to time, data handling first and design second; redo only the recurring error types in the final week.

Three columns: the sentence I wrote, the scheme key words (uncertainty, percentage, line of best fit, controlled variable), and which one was missing. Put the most frequent gap on the first page of your notes and read it before each paper.

The specification has changed, so older practical questions do not always match the current paper: do not start from the oldest year. Build the three answer types on three to five years of current papers, fill gaps with the official specimen, and where years are thin use your own lab reports and data questions.

Is this page a mock paper or a drilling guide?
This is the A-Level Physics 9702 Paper 3 drilling guide: assessment structure, drill order, a 12-week timetable, pacing, common mark losses and the error-log method. For questions with answers, use the A-Level Physics 9702 Paper 3 mock papers linked under Related.

By topic or by year first?
By topic. Eight to ten years of the same topic back to back is what exposes repeating errors; going straight to whole papers just repeats the same batch under time pressure.

How should the error log be written?
Do not copy out questions. Per error record four things: question reference, which step failed (concept, wording, calculation), what the mark scheme requires, and the correct action next time.

Do I really need a percentage uncertainty for every reading?
Yes, because the question asks you to compare. Absolute values cannot show which measurement is more reliable; write uncertainty divided by reading times 100 next to each entry and the comparison writes itself.

Can the gradient come from the first and last points?
Only if both sit on the line of best fit, never the first and last data points; and the steepest and shallowest lines are still needed for the uncertainty range.

Related: practice area · A-Level Physics 9702 drilling guide · A-Level Physics Paper 4 drilling mock