Let's Graph With Probes
Focus for this activity
In this activity, you will be Isabel, and you will use the motion probe to graph Isabel's (and your) movement from the City Library to the Movie Theater, then back to the Library.

Recall that the Movie Theater is 7400 meters away from the Library, but you won't have to move that far in class!

You'll be learning how to graph motion and describe motion mathematically: You'll mark the locations of the Library and the Movie Theater on a "street" designated with masking tape on the floor. You'll then use motion probes to collect data, and computers to graph the motions that you make.

Prediction
You'll be graphing your motion, and we'll be talking about Isabel's positions at the Library and at the Movie Theater.

Before we get started, can you predict Isabel's movement on the graph? Using the pencil tool, (to the right) draw what you think the graph will look like if Isabel travels from the Library to the Movie Theater and then back to the Library. Let's assume for now that the distance between the Movie Theater and the Library is 7400 meters.

When you've finished, please submit your graph for anonymous sharing by clicking the SUBMIT button below the graph.

You may be able to see some of the class' graphs if your teacher chooses several and "releases" them for viewing: You'll see the graphs in a pop-up window that will appear after you click on the Results button below.




Reference points
You may have realized that you need to know where the Library is located, i.e., its position, to get started with your graph. In order to measure positions and distances, a reference point is needed.

For this activity, the reference point will be at position 0, which we'll call the origin. Let's say that the Library is located at the origin.

Isabel will start her trip at the Library, i.e., at position 0, then move to the Movie Theater. You'll also need to know the Movie Theater's position. For this activity, let's say that the Movie Theater is 1 meter from the Library (since you can't walk 7400 meters in the classroom!).

In the next step, your teacher will demonstrate how to find the Library's location, which we've already set and which you need to mark on the masking tape "street". You'll also need to locate and mark the Movie Theater on the "street".


Demonstration
Your teacher will now demonstrate the use of the motion probe, showing you how to find the location of the Library, which we've said will be a the origin, i.e., position 0.

Other positions are measured from the origin. In this activity, the motion is positive if you're moving toward the motion probe, and negative if you're moving away from the motion probe.

Look at the motion graph during the demonstration.



What do you see on the graph when your teacher moves in front of the probe? Nothing changes. Lines and dots jump around on the screen. A line appears on the screen at the end of the movement. A line is slowly drawn across the screen from left to right.
Find the Library!
Set up your motion probe at the end of a desk or table. In the next step, you'll be marking two locations on the masking taped "street", one for the Library and one for the Movie Theater. First, though, you'll need to find position 0, the Library, which is Isabel's starting point.

How do you find position 0? Walk along the "street" in front of the motion probe until you think you've found it, then submit your answer to the following question.

You may be able to see the class' answers if your teacher and "releases" them for viewing: You'll see the answers in a pop-up window that will appear after you click on the Results button below.









How far is the Library from the motion probe? 0 meters .25 to .5 meter .5 to 1 meter 1 to 1.5 meters 1.5 to 2 meters 2 to 2.5 meters 2.5 to 3 meters
What do you see on the graph when standing at the Library? Nothing changes. Lines and dots jump around on the screen. A line appears on the screen at the end of the movement. A line is slowly drawn across the screen from left to right. 4. A line is slowly drawn across the screen from left to right What do you see when standing at the Movie Theater?
What do you see when moving back and forth?
How is the graph different when moving more rapidly vs. more slowly?
Your turn!

Leave your motion probe at the end of a desk or table. Get two Post-It notes and write "Library" on one and "Movie Theater" on the other. Place the notes at two locations along the masking taped "street" on the floor: The Library is located where you and your classmates found position 0 in the previous step. The Movie Theater is located on the "street" 1 meter from the Library. (It's closer to the motion probe than the Library is.)

When you are ready to try out the probe, stand in front of the probe, click the Start button below the graph, then walk along the "steet" in front of the motion probe. Walk back and forth between the Library and the Movie Theater several times, then submit your answers to the following questions.







Your Trip to the Movie Theatre
Now plan and make your trip to the Movie Theater as Isabel did: Start at the Library, proceed to the Movie Theater, then return to the Library. Make one trip, from the Library to the Movie Theater and back to the Library, during the 15 seconds of graphing.

Start the graphing by clicking Start on the motion probe graph. Try this graphing step several times, clicking Clear to erase a previous graph, until you have a graph that you are happy with and willing to share with the class. Then submit the graph for anonymous sharing by clicking on the Submit button below the graph.

You'll be able to see some of the class' graphs after your teacher chooses several and "releases" them for viewing: You'll again see results in a pop-up window that will appear after you click on the Results button below.




Discussing class graphs
Have a look at the class' graphs projected in front of your classroom or in the results pop-up window (that appeared after clicking the Results button at the bottom of the previous page). Please answer and discuss the following questions. You may change your answers after the class discussion.









Are the graphs all the same? Yes No What is similar about the graphs? What is different about the graphs? If you want everyone's graphs to match, what does everyone have to change or agree on?
The End