Now you are ready to plot some sample data. As I’ve mentioned earlier, and as you can see from the example graphs shown so far, the default settings for Excel produce graphs that can be difficult to decipher.
Let’s look at how to construct a decent graph. It would be helpful to you if you can sit down at a computer and construct a graph with me. I’ve found that learning by doing is often much better than learning just by reading.
If you keep your browser to one side of the screen and the Excel to the other, you can keep everything in one spot.
The sample data shown below was collected by allowing a plastic cylinder either fall through or slide down the inside of a PVC pipe, the type often used on the return side of home plumbing below your sink. The pipe had 10 photo gates spaced out at 0.15 m (15 cm) intervals. As the cylinder slides down the pipe, it interrupts the light traveling from a light emitting diode (LED) from one side of the photo gate to a photocell on the other. When the light is blocked, a 5.0 V signal is sent to a data acquisition device (DAQ) and recorded. As the cylinder slides down the tube, it moves faster and faster.
By carefully analyzing the time at which the individual photo gate is blocked and unblocked, and using the measured length of the cylinder, we can calculate the time when the cylinder is approximately halfway past the gate. A plot of this time and the position of the gate allows us to calculate the acceleration. In this particular set of data, the cylinder was held upright, and the object fell through the center of the tube, essentially in free fall.
Copy and paste the data below into Excel. Once there, your data will consist of a single column, which we will need to split.
Free Fall Trial 1
Time (s), Position (m)
To split the data into two columns, do the following:
- Make sure that just your data is selected. It should be in only one column.
- Click on the Data tab, then click on the Text to Columns option.
- In the dialog box that appears, the “delimited” option should be selected. At this point, your screen should look similar to this…
- Click on the [Next>] button.
- A new dialog box replaces the old. Click on the box next to Comma. The dialog box that opens will now look like this…
- Click the [Finish] button to complete the process.
Your data should now be in two columns.
We are now ready to plot your data.