Physics 9702 · AS & A Level · Stress and strain

Stress and strain — practice question

The Young modulus of the material used for a wire is to be determined. The Young modulus $E$ is defined by the equation shown. $E=\dfrac{4FL}{\pi d^2 x}$ A known force is used to extend the wire, and these measurements are taken. Which measurement has the greatest effect on the uncertainty in 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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