Line Graphs

In this experiment, we released the racer from the same height each time and measured how far the racer traveled after one, two, three, and four seconds. The data is averaged, and now we want to create a graph to organize it in a visual, easy to understand way.

So which type of graph works best for this data? Remember, a bar graph compares categories, a pie chart shows parts of a whole. But in this example, we're looking at how the racer's distance changes over time. For that, a line graph works best.

Let's talk about how to set up a line graph. Every graph needs a title and labels to explain what it's showing. I'm going to title this graph, racer movement over time.

The x axis, that horizontal line along the bottom, shows the data that we controlled or preselected. In this case, the number of seconds. Think of it like a number line that begins at zero. Each tick mark will represent one second. It's important to write below each mark and not in the spaces between them.

The y axis runs up and down. This shows what we measured, the distance the racer traveled. To set it up, look at your data. Make sure the range of your data will clearly fit on your graph, then choose equal intervals to count by. Once again, starting at zero. Counting by fives doesn't fit all of our data, but counting by tens works. It helps to select a number that's simple to count by.

Once we set the scale and label all of the tick marks, it's time to plot the data. Don't forget to plot the starting point. That's actually a very important piece of information. At zero seconds, the racer traveled zero centimeters. So the origin zero zero is a point on our graph.

For each of the additional data points, find where the time along the x axis and the distance along the y axis intersect and put a point.

Now here's something interesting. The data table only reaches up to four seconds. However, the racer came to a complete stop before it reached that four second mark. That means at five, six, seven, or any greater number of seconds, the distance wouldn't change. That racer wasn't going to magically move anymore.

Once all of the points are plotted, use a straight edge to connect them. That shows how the racer's distance changed as time went on.

So a line graph is the best way to show how data changes over time. It lets us see patterns clearly. In this case, how the racer's distance increased every second until it stopped moving.