Constructing a line graph
- 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
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 \(\frac{\text{change in vertical amount}}{\text{change in horizontal amount}}\).
