A-LevelPhysicsPhysical quantities and units9702/22 · May/June 2019 · Q14 Marks

1 (a) The diameter d of a cylinder is measured as 0.0125m ± 1.6%. (b) The cylinder in (a) stands on a horizontal surface. The pressure p exerted on the surface by the cylinder is given by p = 4W / (πd²) The measured weight W of the cylinder is 0.38 N ± 2.8%.

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

[A1] absolute uncertainty = (1.6 / 100) × 0.0125 = 2 × 10⁻⁴ m
[A1] p = (4 × 0.38) / (π × 0.0125²) = 3100 N m⁻²
[C1] percentage uncertainty = 2.8 + (2 × 1.6) (= 6%) or fractional uncertainty = 0.028 + (2 × 0.016) (= 0.06)
[A1] absolute uncertainty = 0.06 × 3100 = 190 N m⁻² (allow to 1 significant figure)

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Topic: Physical quantities and units, A-Level Physics (syllabus 9702). Structured question, 4 marks.
Source: A-Level Physics, May/June 2019 Paper 2 Variant 2, question 1.

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