Balancing a loaded metre rule is one of the most common Question 1 set-ups in 9702 Paper 3. By hand, move 10 g masses from the centre to the end of the rule, push the rule along the pivot until it rests level and read the balance point. Tabulate, plot and use the gradient to find the mass of the rule. Every attempt uses a different rule. Allow about 45 minutes.
Past-paper referenceOriginal experiment, wording and numbers, written in the style of Cambridge AS & A Level Physics 9702 Paper 3, Question 1. It is not copied from a past paper.
Practise next: 9702/33 May/June 2024, Question 1 (a balanced metre rule with 10 g masses moved towards one end) · official past papers
Practise next: 9702/31 May/June 2023, Question 1 (a metre rule balanced by springs, with the support position varied) · official past papers
This type of experiment has come up 14 times in the past papers we checked. Show the list
Checked: Cambridge 9702 Paper 3, 2017 to 2019 and 2023 to 2025. Only the papers in our collection are listed, so the real number may be higher. Question papers are available from Cambridge.
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How this question is marked
Measurements (a), (b)
a and the first balance reading to the nearest millimetre.
Table (c)
Six balanced readings over a wide range of n, headings (n has no unit), every p to 0.1 cm and s = 50.0 − p.
Graph (d)
Axes and scales, plotting, the line of best fit, a large gradient triangle and the y-intercept.
Analysis (e) to (g)
P and Q from your own graph with the unit cm, the mass of the rule from P and a, and a genuine limitation.
Habits that save marks
The rule balances over a small range because of friction at the pivot: aim for the middle of it.
Read p directly above the pivot, looking straight down.
A negative gradient is fine: the balance point moves towards the end masses as n increases.
The marking follows the conventions in published Cambridge mark schemes. The experiments, readings and wording on this page are our own.