STRAIGHT LINE GRAPH

Straight Line Graph

The following outlines how to plot a straight-line graph.

The table below shows the distance moved by a car in a period of time going at a constant speed of 12 m/s.

Step 1: Identifying the variables

From the data, we can gather that:

Variable changed: time measured in seconds.
Variable measured: distance moved measured in metres.
Variable unchanged: speed of the car.

Step 2: Labelling X-axis and Y-axis

> X-axis is for variable changed.

Y-axis is for variable measured.

So, we need to label the x-axis and y-axis as below:

Important! Do not forget to include the correct unit for both labels.

Step 3: Choosing the best scale

It is very important to choose the correct scale when plotting a graph. Decide how you want to divide each square on the grid line. Make sure that the value is equal for each square e.g. 0, 1, 2, 3, 4 .... (+ 1 for each square) or 0, 2, 4, 6, 8 ... (+ 2 for each square), etc.

Scale on the x-axis: From the data in the table, the smallest value is 0 and the highest value is 6. This means that the smallest value on your scale should be 0 and the highest is 6.

Scale on the y-axis: From the data in the table, the smallest value is 0 and the highest value is 73. This means that the smallest value on your scale should be 0 and the highest is 80.

Note: Use pencil to do the scales. In case you make any mistakes, you can rub off your work and start again to avoid messy work!

Step 4: Plotting the graph

Once the scales are done, we can now transfer the information from the table onto the graph paper by plotting the points.

Remember to plot the points correctly by drawing a cross ('x') on the exact points. Plotting should be done in pencil.

Step 5: Drawing the straight line graph

After plotting, use a long ruler and align the ruler against all the points and then draw a single straight line across the points. Since this is a straight line graph, make sure the line goes exactly through the points. Use pencil to draw the line.

NOW IT'S TIME FOR YOU TO TRY IT. DO THE EXERCISES BELOW ON THE GRAPH PAPER PROVIDED.