CAIE A-Level Physics Paper 5: The One Most Students Underprepare

CAIE 9702 Physics has five papers. Papers 1–4 test content: mechanics, thermal, waves, fields. Paper 5 tests something different — the ability to plan an experiment you've never seen, and to turn raw data into a clean relationship. That's why it's the paper that decides most A* grades: every content-strong student can do Papers 1–4, but Paper 5 rewards a skill most students never explicitly practice.

The two questions, always

Paper 5 always has exactly two questions. Question 1 (15 marks) is a Planning question — you're given a scenario and asked to design an experiment. Question 2 (15 marks) is Analysis — you're given data from a simulated experiment and asked to analyze it.

Question 1 (Planning): the P2 structure

The Planning question has a rigid mark structure. Every answer earns points in the same six categories:

1. Defining the problem (1 mark) — state your independent and dependent variables explicitly.
2. Method of varying the IV (1–2 marks) — exactly how will you change it, at minimum 6 values.
3. Method of measuring the DV (3–4 marks) — name the apparatus and the measured quantity.
4. Control variables (1–2 marks) — at least two quantities held constant, each with a method.
5. Analysis plan (3–4 marks) — what graph will you plot, what relationship will you extract.
6. Safety and precautions (1–2 marks) — at least one relevant safety point, not a generic one.

Question 2 (Analysis): finding the formula

The Analysis question gives you a data table with roughly 6 rows. Your job is to: (a) identify the relationship between the variables, usually a power law or exponential; (b) manipulate the data so it plots as a straight line; (c) read the gradient and y-intercept; (d) back-calculate the physical constants from them.

The trick to straightening a curve: take logarithms of both sides. If you suspect y = kx^n, take ln of both sides to get ln(y) = ln(k) + n ln(x). Plot ln(y) against ln(x) — straight line, gradient = n, intercept = ln(k). Every Paper 5 Analysis uses this manipulation or one like it.

The uncertainty question

You'll also be asked to calculate the absolute uncertainty in your final quantity. Rules: for sums and differences, add absolute uncertainties. For products and quotients, add percentage (fractional) uncertainties. For powers, multiply the fractional uncertainty by the power.

If y = kx^n,
  (Δy/y) = n · (Δx/x)
  Δy     = y · n · (Δx/x)

Don't forget to round the final answer to the same number of significant figures as your least-precise input. Paper 5 has a "significant figures" mark and most students give it away by over-precision.

How to prepare in 2 weeks

Paper 5 is the one CAIE paper where past paper practice truly can't be skipped. Do 6–8 past Paper 5s in the last two weeks, under timed conditions (1h 15min), then grade yourself line-by-line against the mark scheme. After the first three you'll see the mark structure repeating — that's the point.