Edexcel A-Level Physics Slope and Intercept

Review slope and intercept in Edexcel A-Level Physics through best-fit lines, large-triangle gradients and constants read from graph intercepts.

Exam points

calculate a graph gradient with a large triangle and state the physical constant it represents
read or calculate a y-intercept, then convert a log intercept back to the original quantity
compare a suggested constant with the graph gradient or intercept to judge whether it is valid

[Maximum number: 2]

A student carried out an experiment to determine the Young modulus of a sample of stainless steel in the form of a wire. The student added weights to the wire and measured the corresponding extensions.

The wire had an unstretched length of 2.6 m . The diameter of the wire was $5.6 \times 10^{-4} \mathrm{~m}$ .
The student plotted a graph of weight against extension. The graph showed that the limit of proportionality was not exceeded.

The student's graph is shown below.

Weight / N

Figure for Question C.3.4—Slope and intercept question 1 — Edexcel A-Level Physics AS

Determine the gradient of the graph.

Gradient =

Use of large triangle to determine gradient

(1)

Gradient $=18500\left(\mathrm{~N} \mathrm{~m}^{-1}\right)$ (sf range 18-19, no ue)

(1)

Example of calculation

gradient $=37 \mathrm{~N} \div\left(2 \times 10^{-3} \mathrm{~m}\right)=18500\left(\mathrm{~N} \mathrm{~m}^{-1}\right)$

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C.3.4—Slope and intercept question 1