Motion Detector Lab

Names: __ Period: _______ Date: ______________ Motion Detector Lab Introduction: In this lab, you will use a motion detector, hooked up to a computer to gain experience in interpreting “position vs. time” and “velocity vs. time” graphs. The motion detector uses sound waves to find the distance of an object in front of it at different times. This information is fed into the laptop which uses the software provided to plot the information in real time. Setup: Make sure that both the computer and motion detector are switched on and that the software is running. Take a few minutes to familiarize yourself with the software. Here are some important points: 1. To change number of graphs, go to the Insert menu and select Graph. This will cause a second graph to appear. You can shrink one or both so that one sits on top of the other and you can compare both at once. 2. To change the type of graph, click on the y-axis label and select what you would like to compare. 3. To change the scale of the graph, make sure you click on that graph and click the scale button above. Part 1: Familiarization with the Detector 1. To change the axis range or other graph options click on the Options menu and select Graph Options. 2. Under Axes Options you can change the values for each axis to what you desire. Remember the scale button can also change axis amounts to fit your graph. 3. Set the range of the Time axis to: 0 to 4 seconds. 4. Set the range of the Distance axis to: 0 to 2.5 meters 5. Have one person stand in front of the detector and have someone else push the Collect button in the program. Start to walk back and forth in front of the motion detector when it starts to make noise. 6. Important: There is a minimum and maximum distance for which the detector will work. By moving back and forth, find the minimum and maximum distances. 7. Try collecting data a few times just to get some experience with this setup. Give everyone in the group a chance to try it out. Part 2: Position-Time Graphs 1. For each question below: i. sketch a prediction of the position-time graph in the space provided ii. produce the graph using the motion detector and sketch the result on the same graph in a different color. Important: do not sketch the entire graph produced by the computer, just sketch the relevant part of the graph. a. Start at about ½ meter from the detector and walk away from the detector slowly and steadily. b. Start at about ½ meter from the detector and walk away from the detector, quickly and steadily. c. Start at the 2 meters from the detector and walk towards the detector slowly and steadily. d. Start at the 2 meters and walk towards the detector quickly and steadily. 2. How does the graph made by walking towards the detector slowly compare with the graph made by walking towards the detector quickly? 3. How do the graphs made by walking towards the detector compare with graphs walking away from the detector? 4. Predict the position-time graphs for the situation described below. Sketch your predictions in the space provided and compare your prediction with the rest of your group. Next, produce the position-time graph using the motion detector and sketch the result in a different color. a. Start at about ½ meter from the detector b. Walk away from detector quickly and steadily for 1 second c. Stop for 2 seconds d. Walk towards detector very slowly and steadily for 2 seconds 5. Important: Show and explain the graph produced in part 4 to the teacher moving on 6. Write down the steps necessary to produce the position-time graph shown on the right. From 0 s to 2 s = From 2 s to 3 s = From 3 s to 5 s = 8. Try several times to re-produce the position-time graph shown in question 6. When you think you have it complete show the teacher before you move on. 9. For the graph on the right, use the slope to find the velocity: a. during the first 5 seconds b. during the last 5 seconds Part 3: Velocity-Time Graphs 1. Change the graph to display only Velocity-time graphs with a velocity range from -2.0 m/s to 2.0 m/s. 2. Make velocity-time graphs for each of the types of motion described below. In each case, try producing the graph several times and sketch a reproduction of the graph in the space provided. a. Start at about ½ meter from the detector and walk away from the detector slowly and steadily. b. Start at about ½ meter from the detector and walk away from the detector quickly and steadily c. Start at 2 meters and walk towards the detector slowly and steadily. d. Start at the 2 meters and walk towards the detector quickly and steadily. 3. What is the difference between graphs made by walking away slowly and walking away quickly? 4. What is the difference between graphs made by walking steadily away from the detector and steadily towards the detector? 5. Predict the velocity-time graph produced by the following motion and sketch your prediction in the area provide below. Then perform the actions and sketch the result in a different color. a. Start at the 2.5 meters and walk towards the detector quickly and steadily for 1 second b. Stop for 2 seconds c. Walk away from the detector slowly and steadily for 2 seconds Extra Credit Use the motion detector to reproduce the curved line position-time graphs below as best as you can. Show the teacher when you have completed to see if you earn extra credit