Plotting points and drawing a curve

Plotting measurements

Once you have chosen the axes and the scale, you can plot each measurement as a point. Each point corresponds to a pair of values (x; y), for example (time; distance).

Method

1. Locate the x-coordinate (x) and draw a thin vertical line up to that value.
2. Locate the y-coordinate (y) and draw a thin horizontal line.
3. Place a cross or a dot at the intersection of the two lines.

Example

Time (s)	Distance (m)
0	0
1	5
2	10
3	15

Each row of the table gives a point to plot: (0;0), (1;5), (2;10), (3;15).

Plotting the curve

Once all the points have been plotted, connect them. If the points appear to be in a straight line, draw a straight line using a ruler, passing as close as possible to all the points, without necessarily passing through each one exactly. If the points follow a curved path, draw a smooth, continuous line freehand, without zigzagging between the points.

Common pitfall

Never join the points with broken line segments as in a ‘connect the dots’ game. The curve should represent the general trend of the physical phenomenon, smoothing out the inevitable minor measurement errors.