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Phys 111L Fall 2007
Laboratory 1: Motion in One Dimension
At its most basic level, classical physics describes the motion of objects. The simplest example is that of an object constrained to move backwards and forwards along one line. The task is to track the object’s position relative to a reference point as time passes. One method of representing such motion in one dimension is to graph the position of the object as a function of time. The resulting graph can convey much information about the motion. The goal of this laboratory is to acquaint you with computer based methods for acquiring data representing the position of an object as time passes and to understand graphical representations of motion.
1 Setting up DataStudio for motion detection.
a) Follow the general procedure for setting up the interface as described on page 8. Here the relevant sensor is called Motion Sensor. Before closing the Experiment Setup window, toggle the options in the Measurements tab so that the sensor only collects position data. b) The motion detector works by emitting a series of audible clicks, each of which can be reflected back to the sensor. The sensor can measure the time taken for the round trip and use this to determine the distance from the object which reflected the sound. Start the detector by clicking the Start button. Verify that it produces a series of clicks. Stop the sensor by clicking the Stop button. Now configure the sensor so that it automatically stops after 10 s (see page 8 for details). Check that this works. c) Following the instructions on page 8, configure DataStudio so that it automatically displays a graph of position vs. time. All of your data will be graphed in this window and any number of curves can be display simultaneously. Adjust the vertical scale of the graph so that the maximum is 3 m. It is important in this laboratory that this scale must remain fixed. Follow the instructions on page 8 to do this.
2 Graphical representation of motion. You will now use the motion sensor to track and represent graphically your own motion. When doing so, be aware that the motion sensor does not record correctly when an object is closer than 50 cm from it.
a) Set up the motion sensor so that it will be able to reflect off of you as you move through a range of about two meters. Avoid pointing the sensor toward any other groups. b) Stand stationary at a location between 0.5 m and 1 m from the sensor. Draw a predicted graph of your position vs. time for this situation.
Time
Position
Predicted
Time
Position
Observed
c) Run the motion sensor for a few seconds and observe the graph produced by DataS- tudio. Draw the graph on the diagram above.
d) Repeat parts (b) and (c) for a stationary position between 1 m and 2 m from the sensor. Ensure that you use the same vertical scale for this graph as you did for that in part (c).
Time
Position
Predicted
Time
Position
Observed
e) Describe the main similarity and the main difference between the observed graphs for the two stationary situations and comment on whether the data recorded is consistent with what you observed (visually) regarding your position.
h) Repeat part (f) for the situation where you walk quickly at a constant speed away from the detector starting from a distance of about 50 cm. Ensure that you use the same vertical scale for this graph as you did for that in part (f ).
Time
Position
Predicted
Time
Position
Observed
i) Repeat part (f) for the situation where you walk quickly at a constant speed toward the detector starting from a distance of about 2.5 m. Ensure that you use the same vertical scale for this graph as you did for that in part (f ).
Time
Position
Predicted
Time
Position
Observed
j) In the preceding four exercises, are there any distinct differences between your predicted and observed graphs? If so, explain the discrepancies
k) Describe the main qualitative difference between any graph representing an object moving quickly and any graph representing an object moving slowly.
l) Describe the main qualitative difference between any graph representing an object moving toward the detector and any graph representing an object moving away from the detector.
If you have successfully noticed the differences between the graphs representing mo- tion above, then you have completed a first step in understanding how graphs can provide information about the motion of an object.
e) Printout the three graphs and attach them to the package. Compare the shapes of the three graphs. What are the main differences between them? How could you tell from a graph whether an object moved at constant speed or not?
5 Graphing with Excel In many laboratories in this course, you will use the spreadsheet program, Excel, to manipulate data. The aim of this exercise is to introduce you to graphing with Excel.
a) Use DataStudio to display the numerical data in table form for any constant speed experiment that you have done so far. See page 8 for details on how to do this. b) Open Excel and copy about ten evenly spaced data points into two columns. c) Using Excel’s chart wizard, produce an XY Scatter plot of the data. Add a trend line and the equation for the trend line and determine the slope of the graph. Print out the graph and attach it to this package.
Using the PASCO DataStudio interface and software
- To start a new experiment:
a) Click on the DataStudio desktop icon. This will open a data collection and display window. b) Click Create Experiment. This will open the Experiment Setup window. c) The Experiment Setup window allows you to connect, calibrate and configure the devices and sensors that will gather experimental data. The image of the data interface is clickable at the various ports. Click on the port to which the sensor is connected. For sensors with two plugs connected to digital ports, click on the yellow plug’s port. This will open a window with a list of possible sensors. Click on the appropriate sensor. This opens a tab with settings relevant to just the chosen sensor. d) The sensor can be configured to stop automatically by via Experiment Setup → Sampling Options → Automatic Stop.
- To display data graphically:
a) Drag the data variable name (e.g. Position Ch 1 & 2) from the Data Column into graph in the Display Column. This opens a graph window. b) The window can be rescaled and configured in many ways by double clicking anywhere on the graph. c) The origin can be moved by shifting the cursor so that a “grabbing hand” icon appears. Use this to drag the graph. d) The scale of any axis can be altered by placing the cursor in the vicinity of the axis so that the following icon appears: !. Drag this to adjust the scale. e) Display of the data for any given experimental run can be toggled on and off via the Data pulldown menu. f) The scale of the axes can be fixed for all experiments by double clicking on the graph and opening Axis Settings → Automatic Scaling and can be toggled by clicking the boxes.
- To display numerical data:
a) Drag the relevant data set from the Data Column into the Table entry in the Display Column.
