Graphing Motion - an activity

In Dozer Challenge your group collected data on a constant motion toy - "The Dozer". You plotted a graph of position verses time and found the mathematical model that allowed you to predict the location of the dozer sometime in the future. Your measurements accuracy were limited by your groups coordination and reaction time. Students of science, and for that matter, scientists try to reduce error so what better way then to remove the "human" factor!

Objectives

• Qualitatively analyze the position - time motion of a constant motion toy.
• Qualitatively analyze the velocity - time motion of a constant motion toy.
• Analyze and interpret motion in the kinematics graphs.

Materials:

Preliminary work.

Consider an object that moves away from an observer at a constant speed for 2 seconds, stops for 2 seconds and then travels back toward the observer for 2 seconds.

1. Sketch what you hypothesize the shape of a position - time graph for the above motion.
2. Sketch what you hypothesize the shape of a velocity - time graph for the above motion.

Print out the .pdf file here for your sketches. You will use only the graph page for this preliminary work, the data table page will be used for the analysis of the lab.

Setup:

1. Turn on the laptop and give it a minute or so to connect to the wireless network, while this is going on,..
2. Connect all probes to Labpro and computer THEN start the loggerpro software.
3. Loggerpro should start with a position - time graph and a velocity - time graph on screen.
   

Data collection :

1. Attempt to collect data that is similar that described in the preliminary work. Don't concern yourself if the time is off a little.
2. Note that there is a dead zone of about 30 cm in front of the motion detector, if the cart moves into this area, you will not get data. This will show up as a flat line.
3. To clean up your graphs click on the graphs and CTRL-J to auto scale the graphs
4. Select File ,"Printing options" and put your lab partners names in the dialog box.
5. Select File , Page Setup and select the Landscape button.
6. Print out the graphs, Select, page 1 of 1 only and print copies for each lab partner.

Write up

• Using colored pencils highlight the corresponding areas on the displacement - time and velocity - time graphs.
  • when the cart is moving away from the motion detector (the observer).
  • stationary - if at any time.
  • when changing direction- if at any time.
  • when the cart is moving toward the motion detector (the observer).
• On the data table printout for earlier do the following. (Be sure to show all data and work.)
  • Show mathematically that the slope of the displacement - time graph is the value for the velocity graph when the cart is moving away from the motion detector (the observer). Don't copy all of the data from the data table, select only two locations of the position - time graph.
  • Show mathematically that the slope of the displacement - time graph is the value for the velocity graph when the cart is moving toward the motion detector (the observer). Don't copy all of the data from the data table, select only two locations of the position - time graph.

Additional questions

1. Does the velocity - time graph show a strictly constant velocity for the cart as it returns? Support your answer by citing the velocity -time graph.
2. Go back to your preliminary questions and comment on them.
3. How has your view of modeling motion changed? i.e. where were you incorrect? Comment on this.