Fun With Probes

What do you see on the graph when standing at the Library? 1. Nothing changes 2. Lines and dots jump around on the screen 3. A line appears on the screen at the end of the movement 4. 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 pieces of masking tape and write "Library" on one and "Movie Theater" on the other.
With the tape, mark two locations on the floor: The Library is located where you and your classmates found it. The Movie Theater is in line with the Library and located 1 meter closer to the motion probe.

When you are ready to try out the probe, stand in front of the probe, click the Start button below the graph, then walk around in front of the motion probe. Try it 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 Vijay did: Start at the Library, proceed to the Movie Theater, then return to the Library. Make one trip, from the Library to the Movie Theatre and back to the Library, during the 15 seconds of graphing.

Start the graphing by clicking Start on the motion sensor graph. Try this several times 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.




Discussing class graphs
Have a look at the class's graphs on the next page or projected in front of the class. 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
Focus for this activity
The focus for this activity is a train system.
We are going to be working with a very simple model of a train system, in which there are two stations, Station A and Station B. 

In the model, the train starts out at Station A, goes to Station B to pick up a passenger, and then returns to Station A.

You will be the train, walking from Station A to Station B, and then back, and learning about graphing and how to describe motion mathematically.

You will be using motion probes to collect data, and computers to graph the motions that you make.

Station A and Station B will be locations marked on the floor. 
Prediction

You will be graphing your motion, and we'll be talking about the position of Station A and Position of B.

Before we get started, can you predict what a graph of the train's position will look like? Using the pencil tool, (to the right) draw what you think the graph will look like as the train travels from A to B, then back to A.

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




Reference points

You may have realized that you need to know where Station A is located --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 where position = 0.

In the next step, you will position Station A at this reference point, usually called the origin.

You also need to know Station B's position, which we will find in relation to Station A's position.


Demonstration
Your teacher will now demonstrate the use of the motion probe, showing you how to find the origin, which is where position = 0.

Other positions are measured from the origin. In this activity, positions are positive if they are in the direction of the motion probe from the origin, and negative if they are in the opposite direction 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? 1. Nothing changes. 2. Lines and dots jump around on the screen. 3. A line appears on the screen at the end of the movement. 4. A line is slowly drawn across the screen from left to right.
Find Station A!

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 floor, one for Station A and one for Station B.

First, though, you'll need to figure out where Station A is. Let's say that Station A is at position 0.
How do you find position 0? Walk around in front of the motion probe until you think you've found it, then submit your answer to the following question.






POLLING on multiple choice: Histogram is shared with teacher and students.


How far from the motion probe is Station A? 1. Zero meters 2. Between 0 and .25 meters 3. About .5 meters 4. Between .5 and 1 meter 5. Close to 1 meter 6. About 1.5 meters 7 More than 1.5 but less that 2 meters 8 Close to 2 meters 9. Close to 2.25 meters 10 Close to 2.5 meters 11 More than 2.5 meters
Follow-up: Making and thinking about matching graphs
Now that you have an idea about how to make motion sensor graphs match, try to make one that matches the graph below! Try it several times, then submit your graph for sharing.
<Add data set to be matched to this graph; students then add a second data set generated by their attempt to match the first data set>

FLAG-N: Teacher selects graphs to share with the class.

What was easy to match? What did you have to think about in order for the graphs to match? What was difficult about matching the graph? What do you notice about other students' graphs?
Discussion










Wrap-up
Shown below are three of the position graphs you made (your prediction, the graph that you submitted for your ABA trip, and the graph you submitted when matching a given one.) Think about the graphs and your use of the motion probe and answer the following question. When you are ready to share your answer, click the Submit button.



FLAG-N: Teacher selects some submissions to share with the class.







What did you learn about position and motion?
This is the graph to match - to be changed only by the authors


Is that OK?



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