Paper 3 is two experiments at the bench: Question 1 builds a table and a graph to test a relationship, Question 2 checks a relationship with two sets of readings and asks for limitations and improvements. Each paper below is rephrased from a real past paper, with a realistic set of readings to process: work it part by part, then compare with a worked full-mark answer and the examiner's comments.
Readings to the precision of the instrument (a metre rule to the nearest mm, a stopwatch time over several oscillations), repeated where needed, with enough values over a wide range (usually six).
Column headings with a quantity and its unit (for example T / s), raw readings to the same number of decimal places, calculated values to the right number of significant figures.
A graph with a sensible scale, crosses within half a small square, a line of best fit, a gradient from a large triangle and the y-intercept read or calculated, then the constants with units.
In Question 2: the percentage uncertainty in a reading, whether the results support a relationship, and four limitations each paired with a specific improvement.
The questions on this page are rephrased from a Cambridge International past paper for teaching. The readings, figures, wording of the workout and the worked answers are our own; the marking follows the published mark scheme. The original question paper is available from Cambridge.