# Average Velocity Lab

Teacher's Notes

An important aspect of data collection and analysis is finding the best fit line for the data. In addition, the slope and equation of that line can help scientists predict additional information. During this lab, each student will collect data of themselves walking at a constant velocity. This data will be graphed and analyzed in your math class.

## Objectives

• Use a Motion Detector to measure the position of a student moving at a uniform velocity.
• Construct a distance vs. time graph of the data collected using conventional methods and the TI-83®.
• Analyze the kinematic graph of the students motion.
• Determine the average velocity of the student using the graph.
• Model uniform motion with an algebraic equation.

## Materials

 Power Macintosh or Windows PC Vernier Motion Detector Logger Pro Universal Lab Interface

## Procedure

1. Connect the Motion Detector to PORT 2 of the Universal Lab Interface.
2. Prepare the computer for data collection by opening “Average Velocity Lab” from the experiment files of Logger Pro. An “empty” distance vs. time graph should appear on the screen. Its vertical axis has distance scaled from 0 to 5.0 m. The horizontal axis has time scaled from 0 to 2 seconds. A data table will also appear on the screen with a “Time” and a “Distance” column.
3. One student should stand about 0.4 m from the Motion Detector.
4. Another student should click to begin data collection. The student in front of the motion detector should start walking away from the detector when they hear the Motion Detector start to click.
5. Print, copy, or save your data as instructed by your teacher.
6. To save your data to the floppy drive:
• Choose Export Data from the File menu.
• Choose “3½ Floppy (A:)” from the Save in list box.
• Enter a file name in the appropriate box. Note: A good file name would be “yourlastname_distance.”
• Click the Save button.

## Data Table

 Data point Time (s) Distance (m) Change in Distance (m) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

## Analysis

Most of the analysis that follows will be done in your advanced algebra class. Once completed, turn in to your science teacher.

1. Calculate the change in distance between each of the points in your data table. Enter these values in the right column of the data table.
2. Using conventional methods, construct a distance vs. time graph for your data.
3. Determine the equation for the best fit line for your data.
4. Enter the data into the TI-83® and make a scatter plot of the data.
5. Determine the regression line and its equation in using the TI-83®.
6. Compare the slope of this line to the slope of your best fit line. Determine the percent error of your slope.
7. What are the units for the slope of this line? What quantity is measured in these units?
8. Calculate your average velocity the first and the last time recorded (t and t) using your data and the definition of average velocity:
9. Compare your average velocity to the slope of the regression line from the TI-83®. Determine the percent error of your average velocity calculation.
10. Why do we use the slope of the regression line as the accepted value in the equation for percent error?
11. Why do we get different answers when using different methods of analyzing data?

## Extension

Using the equation for the regression line and assuming the student would continue in this motion, complete the following data table:

 Time (s) Distance (m) 12 7 32 24

Lab and experiment file written by Todd Mickley. Download the Word® document and LoggerPro® experiment file for your use.