Edexcel A-Level Physics Qualitative and Quantitative Uncertainties

Review qualitative and quantitative uncertainties in Edexcel A-Level Physics through limits, percentage differences, scatter and systematic-error judgements.

Exam points

compare uncertainty limits with accepted values to judge whether a material or value is plausible
calculate percentage difference and compare it with percentage uncertainty before concluding
explain how scatter, systematic error or invalid extrapolation affects graph-derived values

[Maximum number: 2]

A student added small lead spheres to a test tube. The student placed the test tube in a small beaker of water. The test tube floated as shown.

Figure for Question 6.5.9 - Qualitative and quantitative uncertainties question 1 — Edexcel A-Level Physics A2

The student gave the test tube a small vertical displacement. The test tube then oscillated vertically.

The student replaced the water with another liquid. The period is given by $T=\sqrt{ rac{16\pi m}{D^2 ho g}},$ where D is the test-tube diameter, m is the mass of the test tube and spheres, and ho is the liquid density.

The density of glycerol is $1260\,\mathrm{kg\,m^{-3}}$ . Deduce whether the liquid could be glycerol.

The upper limit is $1190(1+0.041)=1239\,\mathrm{kg\,m^{-3}}$ , below $1260\,\mathrm{kg\,m^{-3}}$ . Therefore the liquid may not be glycerol.

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6.5.9 - Qualitative and quantitative uncertainties question 1