Edexcel A-Level Physics Hooke’s Law

Practise Edexcel A-Level Physics Hooke’s law through F=kx calculations, spring stiffness, force-extension gradients, series springs and elastic deformation contexts.

Exam points

use F=kx to calculate force, extension, spring stiffness or new spring length
find stiffness from the gradient of the straight-line part of force-extension graphs
reason about changed stiffness for longer wires or springs arranged in series

[Maximum number: 2]

A student carried out an experiment to determine the Young modulus of constantan.
The student had a constantan wire with cross-sectional area A of $3.97 \times 10^{-7} \mathrm{~m}^{2}$ .
The unstretched length x of the wire was 4.00 m.

The student added slotted masses to the wire and determined the corresponding extensions. The student plotted a graph of force against extension, as shown.

Figure for Question 1.4.27 - Hooke’s law question 1 — Edexcel A-Level Physics AS

Show that the stiffness of the wire is about 1.3 x 10^4 N m^-1.

The gradient of the straight-line section is the stiffness. For example, $k=60\,\mathrm N/(4.6\times10^{-3}\,\mathrm m)=1.30\times10^4\,\mathrm{N\,m^{-1}}.$

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1.4.27 - Hooke’s law question 1