Balancing a metre rule is one of the most common 0625 Paper 5 experiments. Place the load, slide the rule along the pivot until it rests level, and read the scale above the pivot through the magnifier. Complete the table, plot your own graph and use its gradient to find the mass of the rule. Every attempt uses a different rule. Allow about 20 minutes.
Past-paper referenceOriginal experiment, wording and numbers, written in the style of Cambridge IGCSE Physics 0625 Paper 5 (Practical Test), Question 1. It is not copied from a past paper.
Practise next: 0625/53 May/June 2023, Question 1 (the mass of a metre ruler using a balancing method) · official past papers
Practise next: 0625/52 February/March 2024, Question 1 (a balancing method for the mass of a metre ruler) · official past papers
This type of experiment has come up 31 times (15 in Paper 5, the Practical Test, and 16 in Paper 6, the Alternative to Practical) in the past papers we checked. Show the list
Checked: Cambridge IGCSE Physics 0625 Papers 5 and 6, 2014 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
Method (a)
A technique that really puts the centre of the load on the mark: line it up from directly above.
Table (b)
Headings with quantity and unit (and no unit for the ratio b / a), balance readings to the nearest millimetre, a and b worked out from each reading, and b / a to 2 or 3 significant figures.
Graph (c)
Axes labelled, sensible scales, accurate plotting and a well-judged best-fit line.
Analysis and evaluation (d) to (g)
A large gradient triangle, the mass of the rule equal to the gradient with the unit g, a conclusion that uses the graph, and how to allow for a centre of mass that is not at 50.0 cm.
Habits that save marks
The rule has some friction on the pivot, so it rests level over a small range. Aim for the middle of that range.
Read the scale directly above the pivot, looking straight down, not from the side.
b / a is a ratio of two lengths, so its column heading has no unit.
Moments: M × a = MR × b, so the graph of M against b / a has gradient MR.
The marking follows the conventions in published Cambridge mark schemes. The experiments, readings and wording on this page are our own.