Introduction to Motion Using Real-Time Data Collection[i]

Purpose: You will learn how to use the GLX and the PASCO motion sensor to make displacement versus time and velocity versus time graphs. You will learn how to relate these two types of graphs as they are frequently used in physics to analyze motion.

Materials: 1 GLX, 1 motion sensor

Procedure:

Using the GLX:

Turn on the GLX or plug it in using the AC adapter.

We will be using the motion sensor. Plug in the sensor to one of the ports at the top of the GLX. A position versus time graph should automatically open.

Press and then . Use the keys to scroll up and down and the to select the information to modify. Change the settings so that Sample Rate Unit is samples/s, sample rate is 20, Smooth Averaging is Off, and position and velocity are visible. After making a change, press the to save the change. Press and then . To view both graphs, go into graphs and choose Two Graphs.

Press the button to begin collecting data. Press it again to stop. The motion sensor will click when it’s taking data. The screen will display the last data values taken. To view previous run, press and boxes will appear around the axis labels. Use the keys to move the highlighting over the Run #X label. Press and scroll to the run you want to see. You may also do this again to return to the latest run. The GLX will retain all your data while you are performing the experiment, BUT remember to save before shutting it down AND if you’re going to connect the GLX to a computer, make sure you save as well. Otherwise, you’re data will be lost and there is no way of restoring it.

If you want to delete a run, make sure it is on the screen, then press to highlight the axis labels. Use the arrow keys to highlight Run #X. Then press and scroll down to “Delete Run.” (Note that if you delete the data from one graph, that run is deleted from every graph.)

For more detailed instructions and more editing features, refer to the Introduction to Using the Xplorer GLX handout.

Making Displacement-Time and Velocity-Time Graphs

For each of the following scenarios, make a sketch of your graph and write a brief description of the motion.

  1. Walk away from the detector slowly and steadily.
  2. Walk away from the detector medium fast and steadily.
  3. Make a sketch (meaning that it does not need to be perfect, but rather just enough so that you know what happened) of both the displacement and velocity graphs putting both the slow and medium fast on the same set of axes for both the displacement and velocity graphs so that you can easily compare the results.
  1. On your sketches, record the following data for the graphs:
  2. The value of the slopes of the lines on the displacement graphs. To get the value of the slope of the line, highlight the whole line (or segment of the line that corresponds to the data that you wish to analyze) and press and scroll to “Linear Fit.” You can see the slope and y-intercept below the graph.
  3. The value of the change in displacement for each of the displacement graphs. You can do this by inspection (i.e. reading the values off the graph) or by keeping the data highlighted and pressing scroll down to “Statistics” the maximum, minimum, and average values appear beneath the graph. By subtracting, you will get the change in displacement.
  4. The average value of the velocity on the velocity-time graph. You can find this by highlighting the data using the same method described above and selecting “Statistics” as above.
  5. The area under the curve for the velocity graphs. Be sure to determine the area under the curve only for the same highlighted area so that you can properly compare your data. Press and scroll down to “Area Tool.” The area for the selected region will appear beneath the graph.
  1. Walk toward the detector slowly and steadily.
  2. Walk toward the detector medium fast and steadily.
  3. Make a sketch of both the displacement and velocity graphs, and record the same information as in part D above.
  1. Describe the difference between the displacement-time graphs you made by walking slowly and the ones made by walking more quickly. Compare the magnitudes (the absolute value) of the slopes of the lines.
  1. Describe the difference between the displacement-time graphs you made by walking toward and away from the detector. Compare the sign (i.e. positive, negative, zero) of the slopes of the lines.
  1. Describe the difference between the velocity-time graphs you made by walking slowly and the one made by walking more quickly.
  1. Describe the difference between the velocity-time graphs you made by walking toward and away from the detector.
  1. Predict the displacement-time graph produced when a person starts at the 1-m mark, walks away from the detector slowly and steadily for 3 seconds, stops for 4 seconds, and then walks quickly toward the detector. Sketch your prediction below.
  1. Predict the velocity-time graph produced for the motion described in the previous question. Sketch your prediction.
  1. Test the predictions you made in parts L and M. Is your prediction the same as the final result? If not, describe how you would to make a graph that looks like your prediction.

Analysis Questions

  1. How does the slope of the line on a displacement-time graph compare to the average value of the velocity on the velocity-time graph? Be quantitative and use the values that you recorded.
  1. How does the change in displacement on your displacement-time graph relate to the area under the curve on your velocity-time graph? Be quantitative.
  1. Is it possible for an object to move so that it produces an absolutely vertical line on a velocity-time graph? Explain.

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[i] This lab meets Massachusetts State Frameworks in Physics for items 1.1 – 1.3