Investigation: How is motion recorded?

Transcription

1 Investigation: How is motion recorded? Introduction In this investigation you are going to discover a way to record your movement and find different ways to represent this recording with a graph. You will make three different types of graphs and learn the properties of each. Terms - Make sure you have an idea of what these terms mean before you begin: Distance. Displacement Velocity Speed Acceleration Group Each group should have the following members: walker, reader, recorder, computer operator. Switch roles after every part (I, II, III, & IV)! Procedures I - Using the Ultrasonic Motion Detector The ultrasonic motion detector works in a way that similar to a bat's sonar system. Sound waves are created inside the box and return to the box when they reflect off of an object. The device then determines how far away the object is based on how long the sound takes to leave the box and return. This process happens over a thousand times every second! The first few activities will help you to understand the abilities of the detector. When you wish to use the detector, launch the "MacMotion" program. At the bottom, there is a button marked Start. When you click on this, the detector will start making noise and collecting data. Every time you click start, new data is taken.

2 Have someone stand a few feet away from the detector, click start, and have that person move forward, backwards, and side to side. You can do this as many times as you need to answer these questions: 1. From the screen, explain what information is being recorded 2. Is there a limit to how close or how far you can get from the detector before is behaves strangely? 3. Is there a limit to how far you can move to the side before you become "undetected"? 4. Does the recorder detect side to side movement? II - Distance v. Time Graphs A. Now that you know how the detector works, try walking at a steady pace towards the detector and then try moving steadily away from the detector. On the analysis sheet, sketch and label (description and axes only! you don't have to mark any numbers!) the two graphs given 1. What is the same about the two graphs and what is different? B. Make two graphs walking towards the detector. You first graph should be slow and steady and the second should be steady, but faster than the first. Sketch and label the results with the two graphs given. 2. What is the same and what is different between the two graphs? 3. If you were to see two unlabeled graphs of motion made by a different group, how would you know which graph showed the faster motion? 4. Could you make the line completely vertical? Why or why not? 5. Predict what a graph might look like if you start 1m in front of the detector, walk away slowly and steadily for three seconds, stop for three seconds, and then walk slowly toward the detector for three seconds. Use the graph given and a dashed line to show your prediction C. Perform the motion described above and record the data on the same graph with a solid line. 6. Is your prediction correct? If not, how would you have to move to match your predicted sketch? 7. Look at the following graph. Explain how you would move to create this graph.

3 Time (seconds) D. Have everyone in the group try to match the graph above. 8. Did you have to adjust your plan from #7 to match the graph? E. Below are two new graphs. Try to walk so that you match the shape each one. P P t t 9. Explain how you had to move in each graph in order to match it. Is there a term for this motion? III. Velocity vs. Time Graphs A. Load the file "velocity vs. time" try walking at a steady pace towards the detector and then try moving steadily away from the detector. Sketch and label the two graphs. 1. What is the same about the two graphs and what is different? B. Make two graphs walking towards the detector. You first graph should be slow and steady and the second should be steady, but faster than the first. Sketch and label the results with the two graphs given. You may have to "smooth" the graph a bit as the lines will be bumpy. 2. What is the same and what is different between the two graphs?

4 3. If you were to see two unlabeled graphs of motion made by a different group, how would you know which graph showed the faster motion 4. Predict what a graph might look like if you start 1m in front of the detector, walk away slowly and steadily for three seconds, stop for three seconds, and then walk toward the detector for at a faster rate. Use the graph given and a dashed line to show your prediction C. Perform the motion described above and record the data on the same graph with a solid line. 5. Is your prediction correct? If not, how would you have to move to match your predicted sketch? 6. Look at the following graph. Explain how you would move to create this graph Time (seconds) D. Have everyone in the group try to match the graph above. 7. How did you adjust your plan from #6 to match the graph? 8. Describe how you moved in each part of the graph. 9. On the way back did you run into the detector? Was there a missing piece of information on the velocity graph? E. Below are two new graphs. Try to walk so that you match each one. V V t t

5 10. Explain how you had to move in each graph in order to match it. Is there a term for this motion? IV. Predict velocity from position 1. Using the given position graph, try to determine what the corresponding velocity graph might look like. Sketch your prediction with a dashed line. A. Open the file "PV Match". Try to match the graph. 2. Did your prediction match? What changes did you need to make?

6 Investigation: How is motion recorded? Analysis Sheet Name Period: Part I: 1. From the screen, explain what information is being recorded. 2. Is there a limit to how close or how far you can get from the detector before is behaves strangely? 3. Is there a limit to how far you can move to the side before you become "undetected"? 4. Does the recorder detect side to side movement? Part II: Sketch of position-time graphs. Title: Title: 1. What is the same about the two graphs and what is different?

7 Second pair of position -time graphs. Title: Title: 2. What is the same and what is different between the second pair of graphs? 3. If you were to see two unlabeled graphs of motion made by a different group, how would you know which graph showed the faster motion? 4. Could you make the line completely vertical? Why or why not? 5. Predict what a graph might look like if you start 1m in front of the detector, walk away slowly and steadily for three seconds, stop for three seconds, and then walk slowly toward the detector for three seconds. Use the graph given and a dashed line to show your prediction Time (seconds)

8 6. Is your prediction correct? If not, how would you have to move to match your predicted sketch? 7. Look at the following graph. Explain how you would move to create this graph. 8. Did you have to adjust your plan from #7 to match the graph? 9. Explain how you had to move in each graph in order to match it. Is there a term for this motion? Part III: Sketch of velocity-time graphs. 1. What is the same about the two graphs and what is different?

9 Sketch of velocity-time graphs. 2. What is the same and what is different between the two graphs? 3. If you were to see two unlabeled graphs of motion made by a different group, how would you know which graph showed the faster motion 4. Predict what a graph might look like if you start 1m in front of the detector, walk away slowly and steadily for three seconds, stop for three seconds, and then walk toward the detector for at a faster rate. Use the graph given and a dashed line to show your prediction Time (seconds) 5. Is your prediction correct? If not, how would you have to move to match your predicted sketch?

10 6. Look at the following graph. Explain how you would move to create this graph. 7. How did you adjust your plan from #6 to match the graph? 8. Describe how you moved in each part of the graph. 9. On the way back did you run into the detector? Why do you think this happened? Was there a missing piece of information on the velocity graph? Does this say anything about what velocity graphs tell you? 10. Explain how you had to move in each graph in order to match it. Is there a term for this motion?

11 Part IV: 1. Using the given position graph, try to determine what the corresponding velocity graph might look like. Sketch your prediction with a dashed line Time (seconds) 2. Did your prediction match? What changes did you need to make?