Physics 253 Fundamental Physics Mechanic, September 9, Lab #2 Plotting with Excel: The Air Slide

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1 1 NORTHERN ILLINOIS UNIVERSITY PHYSICS DEPARTMENT Physics 253 Fundamental Physics Mechanic, September 9, 2010 Lab #2 Plotting with Excel: The Air Slide Lab Write-up Due: Thurs., September 16, 2010 Place of meeting Altgeld 100 Read Giancoli: Chapter 2 Introduction and Assignment This is a continuation of the Air Slide lab you did last week. You are to use the presentation techniques learned in this computer lab to repeat the write-up of the air slide laboratory. You ll learn how to organize your lab report, create equations with Word, and tables and plots with Excel. If you are already familiar with Word and Excel, you can use the laboratory time to write up your lab. However, if you choose not to stay for the assigned laboratory period, you must sign-in before leaving. Next week hand in your redone laboratory report according to the instructions given in the Lab Write-Ups and the Data Analysis sections below. Laboratory Log Book All students are to bring to laboratory a quad-ruled notebook. The book serves as a record of all activities, data, and analyses. Believe it or not these are still de-rigor for laboratory activities! The first things that you should write in your lab notebook before you start are: (1) your name, (2) the date, (3) a list of the names of your lab partners and (4) your lab TA s name and Section #. This should all be written in the upper right hand corner of your lab notebook. Example (placed in upper right hand corner) Sean Kingston Jan. 21, 2009 Lab Partners: Jay Sean Elvis Costello Al Younkovich Lab TA: Zac Brown, Section A

2 2 Lab Write-ups Lab write-ups are to be done on a computer. In this lab we will demonstrate Word and Excel, but you may use any other similar document and spreadsheet programs. I. The first page of your lab write-up must have the name block (word for word) as in the upper right hand corner of your lab notebook (name, date, lab partners, etc.). II. III. The title of the lab follows next. A graph or diagram detailing the experimental setup with explanatory text. Example: Air slide diagram (a) Open up the Word 2007 application. (b) Select the insert tab, then click on shapes in the Illustrations section. Then select the triangle and draw it in your word document. By pulling on the small icons you should be able create a right triangle. Next select the rectangle and draw the basic block on incline diagram below. Notice that you can rotate the objects by moving the green dot (that appears when you select the object). To rotate the object by a fixed amount, right-click on it and select Format AutoShape. Click on the size tab and insert your desired rotation angle (useful to get the block to be parallel with the surface of the incline). When the block is selected, you can also move it by small amounts by using the arrow keys (up, down, sideways). IV. Next follows the objective of the lab, which is a brief explanation of what the lab is all about. V. Next, the data should be presented in the exact order collected. For a repeated sequence of data, such as velocity and time, the data should be entered and presented in table format. Example: Tables.

3 3 (a) Select the insert tab, then click on table in the Tables section. Select insert table and create a two column by eleven row table by providing the row and column information. (b) The table should have a title. The first row of the table should describe the data (position, velocity, etc.), its units, and any other important information you wish to enter. You can change the height of the rows and width of th ecolumns by holding the cursor over a border in the table until it changes into a double arrow, then click and drag to make the row or column wider or narrower. You can change the borders by going to the Design tab, then the Draw Borders section, selecting the line weight icon, and changing the weight to a heavier weight (like, from ¼ pt to 3 pt), and then clicking on the border you wish to modify on the table. To center the text in a cell, select the text so that it is highlighted, right-click on the highlighted text, select cell alignment, and pick the icon that centers the text. (c) Finally, give your table a title, as shown in the example below: Velocity as a function of time Time (sec) Velocity (m/sec) VI. For each lab report, next follows the Results or Data Analysis section. Formulae If you are asked to make a calculation, first write the formula, then the formula with the appropriate numbers (and their units) substituting the variables, and then the final number with the appropriate number of significant figures and units. Example: Parabolic trajectory. Calculate the position of a particle at time t = 3 sec starting from rest undergoing an acceleration of g. (a) To write the formula, select the insert tab, then click on equation in 2 the Symbols section. Type the following equation: x = 1 at 2

4 4 (b) Next, substitute the variables with their corresponding numerical values and units: x = (1/2)at 2 = (1/2)(9.8m/s 2 )(3s) 2 = 44.1m 40m This is how all calculations should be shown in the Data Analysis section of your lab write-up. Plots The best way to present tabulated data is with a table, Excel offers a useful tool for plotting information. Open up the Excel 2007 application. Label column E time and the column F position. (Be sure to use these columns as the directions that follow might be different particularly if columns A and B are used!) In the time column, insert the values from 1 to 10 in steps of 1. In the position column insert the square of the time values: 1, 4, 9, 16, 25, 36, 49, 64, 81, and 100. To plot this data go to the insert tab, select scatter in the Charts section, and then click on the scatter icon which has no curves. You will get an empty chart region. Then select select data in the Data section. You should get the following dialog box:

5 5 Click on the Add button, which will give the following dialog box: For the Series name, type in: Position Versus Time. For the Series X values, click on the selection tool (the far right icon which has the red diagonal arrow). You will get another dialog box: Then, select the points for the horizontal axis by highlighting the data in the time column. Then press return (or enter). For the Series Y values, click on the selection tool. Then select the points for the vertical axis by highlighting the data in the position column. Then press return (or enter). You should get the following plot. Enter OK twice to clear the dialog boxes.

6 6 (If you are seeing a curve plotted through the data points, select Change Chart Type in the Type section. Select the scatter with only markers icon in the XY (Scatter) section. Press ok. Data points should have no curve or line connecting the points.) Error bars will be discussed shortly. For the following two paragraphs be sure the graph has been selected by left clicking on the graph. That is, the graph should have a blue frame, indicating that subsequent operations impact the selected graph. Go to the topmost layout tab and select the axis titles in the Labels section. Properly label the x and y-axes as Time (sec) and Position (m) always making certain you write out their units. Give the chart the title Position verses Time by selecting the chart title in the Labels section. Click on error bars in the Analysis section, select more error bars options, and set the percentage to 15 % (a large amount, but the error bars become easily observable). If you get horizontal error bars, click on one of the longest horizontal error bar line segments which will select all horizontal error bars (make certain not to select the vertical error bar line segment), and press backspace (or delete). Data should not be plotted with horizontal error bars. Plots made in this way can be cut and paste into your word document. To make multiple plots, add a new time and position column as shown below. Select the design tab, then click on select data in the Data section. Click on the add button and type in a series name (call it position2). In the Series X values field, click on the far right data selection icon and then select the x-data in the time2 column, then press return. In the Series Y values field, click on the far right data selection icon and then select the y-data in the position2 column, then press return. This should produce the two plots on one graph (you will need to

7 7 know how to do this for your final lab writeup, as you will see below). Enter OK twice to clear the dialog boxes. A linear regression is the formal name for a fit to the data which minimizes the distance between the final or best curve and the data points we will learn more about this in later labs. To perform a linear regression fit to the parabola, enter data as shown in the figure below into your excel spreadsheet. Create a plot of your data. Then go to the layout tab and select trendline in the Analysis section. Select more trendline options, then select polynomial and set the order to 2 (a parabola). Also check the box display equation on chart. For the trendline name, select the custom button and type in: Parabolic Fit. Then press the close button. You should be able to reproduce the graph shown below.

8 8 Data Analysis for Air-Slide Laboratory 1) Using Excel, plot position versus time for the three sets of position data. Plot all of them on the same graph. Units are in meters and seconds. Plot appropriate error bars assuming that the detector can measure the position of the cart to within an uncertainty of ± 5%. Fit each plot with a polynomial of order two, and write down the value of the acceleration that you get from your fit. Put these plots in your word document. What do the other coefficients in your fit represent? 2) Do the same for the velocity and acceleration data with the proper units and ± 5% uncertainty. Fit the velocity plots and get a value for the acceleration, move these into your word document. What do the other coefficients in your fit represent? 3) For the first inclination angle, using Equation 2 in the Theory section of the Air Slide lab of last week, plot position versus time using the actual acceleration, ag = sin!. On this same graph, plot your actual measured data (from step [1]) with error bars. Do the same for the other two inclination angles. Include the plots in your word document. VII. Discussion. Is everything consistent? Why or why not? Discuss your results and interpret your data. You are encouraged to discuss these questions with your lab partners and others, but your final answer and conclusions should be in your own words. Duplication of your lab partner s answers is unacceptable.