III. Measuring g, Using Pasco

In part 1, you determined the acceleration due to gravity from Sparky. You will now determine the acceleration due to gravity using the Pasco interface and what is called a picket fence. There are subtle differences between each experimental setup and analysis, which we want to consider.

Plug in the photogate digital sensor into the Pasco interface digital channel #1. Double-click the DataStudio icon to start the program. Click create experiment.  You must now tell the interface what you have just connected; we want Photogate and Picket Fence.  Click on digital channel #1 on the interface picture and choose the Photogate and Picket Fence icon from the sensor menu.  Double click on the Photogate and Picket Fence iconThis will attach the correct sensor to the interface box and open a measurements tab.  On the measurements tab, deselect the position measurement.

Usually we are interested in the data values from our experiment, which we import to Excel for analysis. This time we just want a graph as we have already completed data analysis with the data from Sparky. Here we want velocity and acceleration graphs. In the display window drag and drop the graph icon to the Photogate and Picket Fence icon. By default you will see a Velocity vs. time graph. We want an acceleration vs. time graph also, so you must drag this data from the data window and drop it onto the graph, staying away from the axes. (You should see a dotted rectangle around the graph window and not a dotted rectangle in the graph axes as you drop the acceleration data.) You should now have velocity and acceleration graphs showing on screen.

 

Click the start button to run the experiment; drop the Picket Fence through the photogate so that the fence passes through without hitting the photogate. Now click the stop button and look at the data. There is a button on the left that will allow you to view the data full screen .

Click in the v vs. t graph and choose the Fit button , and a linear fit. Now click in the a vs. t graph and click on the S button , deselect apply to all, and choose mean and standard deviation. With the graph highlighted, print out your graph (under the File menu).

Report your value for g.  Compare this value with the one found in part II and with the accepted value.

At this point we could take more data (after all, this only takes a fraction of a second) or import the data to Excel for further analysis. We are not going to do this.

Instead, consider the differences between the two experiments. Could you use the procedure used with the Sparky data to analyze the data from the Pasco Picket Fence? Why or why not? If you can answer this, you understand why, for all its faults, we still use Sparky.