Constructing a line graph

An empty graph. The y axis is labelled Dependent variable (what is measured). The x axis is labelled Independent variable (what is changed).
  • The independent variable is shown on the \text{x}-axis and the dependent variable is the \text{y}-axis.
  • Variable A might be the weight added to a spring (N) and variable B might be the length of the spring (cm).
  • The graph must have linear \text{x} and \text{y} axes – each square must go up by a regular amount each time.
  • Each axis must be fully labelled with the correct unit.
  • The graph drawn should be scaled so that it occupies at least half of the graph paper in both directions.
  • The intervals on the {\text{x}} and \text{y} axes should not go up in 3 s, 6 s, 7 s, or 9 s, use 1 s, 2 s, or 5 s and multiples of these, for example 10 s, 20 s, 40 s, 50 s are good as they are easy to plot and read.
  • Connect the plotted points with a ruler to draw a best line or curve of fit. No dot to dot joining.

The graph gradient

A graph titled Line of best fit gradient. The x axis is labelled Height (cm), the y axis is labelled Weight (kg). A line runs through various points on the graph. The gradient is calculated as 1.2

You might be asked to find the gradient of the line graph to find a quantity such as the spring constant or the acceleration of a vehicle.

To do this you will need to make a large triangle on the graph and find the vertical and horizontal parts of the triangle.

The gradient is the \frac{\text{change in vertical amount}}{\text{change in horizontal amount}}.