Physics 9702 · AS & A Level · Errors and uncertainties

Errors and uncertainties — practice question

The Young modulus of a wire’s material is to be determined. The Young modulus $E$ is given by the equation $E = \dfrac{4Fl}{\pi d^2 x}$. A known force is used to stretch the wire, and these measurements are recorded. Which measurement contributes the greatest uncertainty to the calculated value of the Young modulus?

  • Alength of wire before force applied, $l = 2.043 \pm 0.002\,\text{m}$
  • Bdiameter of wire, $d = 0.54 \pm 0.02\,\text{mm}$
  • Cforce applied, $F = 19.62 \pm 0.01\,\text{N}$
  • Dextension of wire with force applied, $x = 5.2 \pm 0.2\,\text{mm}$

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