Lab Report Format – Honors Freshman Physics

3_1Lab_Report_Format_HFP_08.pdf

Lab Report Format - Honors Freshman Physics Rice/de la Paz-08 Page 1 Lab Report Format - Honors Freshman Physics Full laboratory reports for this course should include each of the following items in the order described in this document. Make sure that each section and subsection is labeled with the section and subsection headings. Do not number the sections or subsections Section 1 - Title Page The title page should include each of the following items: 1. Title of the experiment. The title should be descriptive of the experiment that was (is to be) performed. I personally enjoy lab titles which describe the lab in a creative or humorous way. 2. Name of experimenter/report author. This is YOU! Since you will be including the names of your lab partner(s), make it clear that it is your lab report. 3. Date. This should list the date(s) that the experiment was performed. 4. Lab Partners. This should list the names, first and last, of each of the students with whom you performed the experiment. Section 2 - Introduction The introduction section should include the items in the list that follows. 5. Purpose of experiment. This section is one of the most important sections of the writeup. In the purpose section you should clearly state your objective for the experiment. In general this should tell what you are trying to find, determine, show, verify, etc. Make it clear what you are trying to do and basically how you plan to do it. Sometimes the purpose of the experiment may be stated as a particular problem that you are trying to solve with the experiment. You will specifically address your purpose in the first section of your conclusion. If there are multiple parts to the purpose, you should state each part of the purpose separately. Example: The purpose of this experiment is to determine how a battery powered car traveling on a level surface moves. We will describe the motion by measuring the position of the car in equal units of time, analyzing the graphs of the data, and by finding a relationship between position and time for the car. 6. Hypotheses. Basically, a hypothesis is your best guess/prediction as to what the results of your experiment might be. This could be stated in an if/then or similar mode. A hypothesis will help guide you as you design and carry out an experiment to fulfill your purpose. These must be generated before performing the experiment. When I have described an experiment for you in advance of the lab, I will expect that you have generated hypotheses consistent with your purpose prior to beginning the lab. I will frequently check to see that you have done so by asking you to submit your hypotheses or by giving you a quiz in which you have to restate your hypotheses. If there are three major parts to an experiment, you should generate a separate hypothesis for each part of the experiment. Note that there is no pressure on you to have a "correct" prediction in your hypothesis. You should certainly never bias your experiment to try to make your hypothesis "true." Example: As the mass hanging on the end of the pendulum increases, the time required to complete a swing of the pendulum will increase. 7. Equipment Used (Apparatus). Note that the word is equipment, not equiptment. Make a complete list of the equipment necessary to perform the experiment the way you performed the experiment. 8. Diagram/Description of experimental setup. You should always include a diagram of the physical layout of the apparatus for your experiment. You are not required to be an excellent artist. You are, however, expected to make a neat, and properly descriptive diagram. Use a straight edge for straight lines. Label all parts of your diagram. If the diagram does not "stand alone" to describe how to set up the equipment, you should include a written description of the experimental setup to supplement your diagram. 9. Procedure. Write a brief procedure that describes how to perform the experiment you have described in your purpose and hypotheses. This can be a set of steps or a written narrative. Keep it to the point. Please don't bore me with pages and pages of description of the procedure.

Lab Report Format - Honors Freshman Physics Rice/de la Paz-08 Page 2 Section 3 - Data and Analysis The Data and Analysis section should include each of the following items, in the order listed: 10. Raw Data. When you performed your experiment you recorded your data in some organized form. Because you never know when a piece of data you thought was bad turns out to be good, you should keep all data you collected in a reasonably organized fashion. Raw data should be collected in ink to reduce the temptation to erase seemingly bad data. This should be included after the procedure before the formal data table and graphs. You may use ink on other parts of the report if you wish, but I suggest pencil. 11. Data Table. The data table should be neatly laid out with each variable heading a column including the units of measurement. Data should be displayed in columns (not rows) to the correct number of significant figures for the instruments and techniques used in its collection. Data tables should be titled with some sort of descriptive title making it clear which part of the experiment the data represents. Data tables should have lines (drawn with a straight edge) which separate columns and which offset the title, variable descriptions and and unit descriptions from the data. There is no need to include units on each entry in the data table if the units have been specified in the column heading. Pay attention to standard conventions for the placement of the independent variable (left most column) and the dependent variable (to the right of the independent variable). Sometimes it will be more convenient to use abbreviations to describe the quantity in some or all of the columns of a data table. If you use abbreviations, be sure to specify exactly what your abbreviations represent. Include, near your data table, a description of the values of quantities which were held constant in the experiment. This will be very important when you attempt to determine the significance of the constant of proportionality of the graphs. 12. Sample Calculations. Many values in your data table may not actually be collected data but may rather be the result of some manipulation or calculation of the data collected in the experiment. You do not have to show each individual manipulation and/or calculation if you will show one example of each manipulation or calculation with some description of what is being done and with some reference to which column of the data table is being demonstrated by the sample calculation. Don't forget to show the equation(s) used in calculations (if you used one) and to include units throughout the calculation, Sample calculations are required for every column of your data table that is the result of a calculation, no matter how simple. Make these calculations on the same page as your data table so that they are easy to find. Label this section: SAMPLE CALCULATIONS. Each sample calculation should include a written description and or symbolic representation of the calculation to be done. This should be followed by substitution of a specific data point from the raw data (including units) into the symbolic representation (equation). Finally you should calculate the value and show how the units work out (dimensional analysis.) 13. Graph(s). For each relationship that is being investigated in your experiment, you should prepare the appropriate graph. In general your graphs in physics will be scatter graphs. The graphs will be used to both solidify a conceptual understand of the relationship but also to develop a mathematical statement which describes that relationship. If your graph does not yield a straight line, you will be expected to manipulate one (or more) of the axes of your graph, replot the manipulated data, and continue doing this until a straight line results. In general it should never take more than three graphs to yield a straight line for this course. Graphs will be checked for each of the elements described in class (and in the Student Guide to Graphical Analysis) as essential for good graphing. These include: a. A title which describes the experiment. For example, if the graph shows the distance moved by a rolling ball as a function of time, and distance is the dependent variable and time is the independent variable, a good title might be POSITION vs. TIME FOR A ROLLING BALL.

Lab Report Format - Honors Freshman Physics Rice/de la Paz-08 Page 3 b. A graph which fills the space allotted for the graph. In general you should have one graph per side of a sheet of graph paper and the graph should be as large as the paper and proper scaling techniques permit. c. The graph must be properly scaled. Scale each axis so as to take up a maximum amount of the space available yet still maintaining divisions which will make plotting the graph as easy as possible. Follow the 1, 2, 5 rule (see Student Guide to Graphical Analysis) when scaling your graphs. d. Each axis must be labeled with the quantity being measured and the units of measurement. If the graph has time squared on the horizontal axis, the horizontal axis should be labeled: TIME2 (s2). e. Each data point should be plotted in the proper position. You should plot a point as a small dot at the position of the of the data point and you should circle the data point so that it will not be obscured by your line of best fit. These circles are called point protectors. f. A curve of best fit. This line should show the overall tendency of your data. If the tendency is linear, you should draw a straight line which shows that tendency using a straight edge. If the tendency is a curve, you should sketch a curve which is your best guess as to the tendency of the data. This line (whether straight or curved) does not have to go through all of the data points and it may, in some cases, not go through any of them. Do not, under any circumstances, connect successive data points with a series of straight lines, dot to dot. This obscures the overall tendency of the data that you are trying to represent. g. If you are plotting the graph by hand, you will choose two points for all linear graphs from which to calculate the slope of the line of best fit. These points should not be data points unless a data point happens to fall perfectly on the line of best fit. Pick two points which are directly on your line of best fit and which are easy to read from the graph. Mark the points you have chosen with a +. h. Do not do other work in the space of your graph such as the mathematical analysis. 14. Mathematical Analysis. In this section you will find an equation which describes the relationship between the variables for each straight line graph that you have plotted. If the relationship is a direct proportion (a straight line graph through the origin) you should follow steps on the left. It the relationship is any straight line which is not a direct proportion you should follow the steps on the right. DIRECT PROPORTION LINEAR GRAPH, NOT A DIRECT PROPORTION a.

r x  position r x  position t time t time b. r x ∝ t y=mx+b c. r x = k·t r x=kt+b d. k= ! r x !t k= ! r x !t e. k=

23.2m!10.7m

12.0s!5.3s

k=

23.2m!10.7m

12.0s!5.3s

f. k = 1.87 m/s k = 1.87 m/s b = 1.00 m g. r x=1.87 m s t r x=1.87 m s t+1.00 m

Lab Report Format - Honors Freshman Physics Rice/de la Paz-08 Page 4 Section 4 - Error Analysis The error analysis section will always include a qualitative discussion of sources of error and will, when appropriate, include a calculation of the absolute and relative error. 15. Sources of Error. This section should discuss any factors which could have affected the results of your experiment. Be specific. It would be unacceptable to list "human error" as a source of error. It would be reasonable, on the other hand, to list the reaction time associated with starting and stopping the stopwatch as a source of error. Sometimes the error will be unavoidable because it is systematic. In other words it is a direct result of the method or equipment used for collecting data in the experiment. If the method could be replaced with one which gives as good or better results without the built-in error, you should suggest such an improvement in the procedure of the experiment. Sometimes the error is avoidable because it is the result of poor measuring on the part of the experimenter. While you should avoid the latter type of error, you should report all possible sources of error in an experiment. 16. Error Calculations. Where there is an accepted value for a quantity which you are determining in an experiment, you should include a calculation of the absolute error and the relative error in the experiment. For instance, let's say the slope of a velocity vs. time graph represents the acceleration due to gravity, and the accepted value for this quantity is 9.80 m/s2. The slope of your velocity vs. time graph yields an experimental of 9.92 m/s2. Make sure that you describe how you determined the experimental and accepted values, The calculation of the absolute error and relative error would be as follows: Experimental Value = slope of velocity vs. time graph Experimental Value = 9.92 m/s2 Accepted Value = acceleration due to gravity on earth Accepted Value = 9.80 m/s2 (Determined from Hewitt textbook, Conceptual Physics, page 18.) ABSOLUTE ERROR Absolute Error = accepted value - experimental value

Absolute Error = 9.80

m s 2 !9.92 m s 2

Absolute Error = -0.12

m s 2

Absolute Error = 12

m s 2 RELATIVE ERROR Relative Error =

Absolute Error

Accepted Value

Relative Error =

0.12 m s 2 9.80 m s 2

Relative Error = 0.012

Relative Error = 1.2%

Lab Report Format - Honors Freshman Physics Rice/de la Paz-08 Page 5 Section 5 - Conclusions This is the most important part of your lab report. It will be worth a major portion of the credit on the lab. You should devote considerable thought and effort to this section of every lab report. This section should summarize the results of the experiment, discuss thoroughly the relationships found, and support any statements made with direct evidence from the experiment. 17. Restate your purpose. Your conclusions should begin by addressing the purpose you originally stated in the introduction. If there are multiple parts to the purpose or multiple purposes, be sure to address each of them 18. Restate your hypotheses. Make sure that you have as many hypotheses are there are parts to the purpose. 19. Briefly describe the experiment. This does not require the same level of detail you provided in the procedure described in the introduction to the experiment. Be succinct. 20. Describe your observations. What were the results of your experiment? What was the trend of the data? What relationship is shown by the graph(s)? What is/are the mathematical model(s) (equations) that come from your graph(s)? 21. Draw Conclusions and support them. What is your answer to the question and how do your observations support it? What do your data/analysis of data tell you about the answer to your question? How do you know? It is not enough to draw a good conclusion. Any concluding statement that you make should be backed up by specific evidence from your experiment. Make it clear what part of your experiment and/or analysis allows you to make the statement. What is the specific evidence from your experiment that allows you to conclude what you have concluded? What is the physical significance of the slopes or y-intercepts of your graphs? Does your analysis of the data support or refute your hypothesis? How do you know? Have you addressed all parts of the question(s)/problem(s)/purpose(s) associated with this experiment? 22. Summarize your results. Make sure that your conclusion has included a thorough discussion of all relationships shown by your experiment, carefully traced from their experimental beginnings through the graphical and mathematical analysis of the data to the derivation of the equations and the establishment of a scientific principal. This section should tie the relationships shown by your experiment together in a logical flow which demonstrates and supports your conclusion statements. Don't leave anything to the imagination of the reader. Make it absolutely clear what you have found out in the experiment and leave no doubt as to how you were able to determine that it was true! Lab Report Format You are free to submit your lab reports in looseleaf form either word-processed, handwritten, or some combination thereof. Feel free to combine computer-generated work with hand-done work. There are certain parts of the lab report for which a computer will be of great help and will save you time. Computer generated graphs and long sections of text like purpose, hypotheses, procedure and conclusions are good examples of this. There are other parts of the report where using the computer might make it look better, but doing so will add significant amounts of time to the process. Creating equations and certain types of diagrams are examples of this. Use your own judgment as to what will allow you to prepare a well organized, easy to follow, legible lab report, while not taking an unreasonable amount of time to prepare.

Lab Report Format - Honors Freshman Physics Rice/de la Paz-08 Page 6 Computer Graphing After we are certain that you understand the basics of graphical analysis, you will be encouraged to use a computer to generate graphs for your lab reports. While the time spent initially to learn to do this will make your first attempts take longer than hand prepared graphs, after a few tries you will be saving yourself a lot of time. This will be especially true if you ever make an error and have to redo a set of graphs. On the computer, corrections can be made quickly and new graphs generated with very little effort. The same cannot be said for hand-prepared graphs. There are a number of appropriate graphing programs which are useful for this course. a. LoggerPro. This is the program that we will use in class when we use the computers for data collection. It also includes a manual data entry option which makes it possible to enter your own data so that you can make and analyze graphs of the data. The school has a site license to this program, which includes use on student computers at home. I will trade you a blank CD for a CD with the program on it. Updates to the program can be downloaded from http://www.vernier.com for free. This program is available in a Windows and a Macintosh version, both of which will be on your CD. The best part is that the files from the two platforms are compatible. This means that if you were to generate a graphing file at home on a Windows machine, you could save it on a disk and load in onto a Mac at school. For this reason, getting yourself a USB drive (thumb drive, jump drive, key drive, etc.) is essential so that you can transport your work between home and school. b. Microsoft Excel. Microsoft Excel is capable of producing the types of graphs used in this course. The learning curve for producing acceptable graphs in Excel is quite a bit steeper than for Logger Pro. Excel is available on the computers in the physics lab, and the files made on a Macintosh can be read on a Windows machine and vice versa. Excel is also much more versatile than Logger Pro for producing data tables. You can also copy data (using the clipboard on the computer) from Logger Pro and paste it into Excel. I personally prefer to make my formal data tables in Excel even though I usually produce my graphs in Logger Pro. c. Other Programs. There are many programs that could be used to do graphing of the sort that is done in this course. Many spreadsheet programs have built-in graphing capabilities and you may find that you can produce acceptable graphs with them. There are a few things that I like to see on computer-generated graphs. If there are required elements of graphs that your program won't accommodate, feel free to add them manually by hand. • A title. • Labeled axes and units • A background grid • A curve of best fit (COBF) • Point protectors • Calculation of slope for linear graphs One of the nicest things about using the computer for graphing is that it will apply standard statistical techniques to calculate the best "regression line" for any set of linear data. This is the same concept as the "curve of best fit." The computer will also calculate the slope of the line for you. When doing your mathematical analysis of the graph, show each of the steps except substitution of numbers for the calculation of the slope. If the computer calculated the slope, say so, and report the results of the computer calculation. Remember, you will have to wait to use the computer for making graphs until you have been given permission by your instructor

Lab Report Format - Honors Freshman Physics Rice/de la Paz-08 Page 7 Lab Report Grading This document has been prepared to give you a good idea about what is expected for lab reports. You should refer to it regularly to make sure that you are including all of the essential parts of each report. Another reason for the preparation of this report is to make the grading of lab reports more efficient. I will refer to it when grading your reports, citing specific sections and item numbers when something is missing, incomplete, or unclear in your report. For instance if on your graph I were to write 13f, you should look at item 13f in this packet. You would find that 13f discusses the line of best fit on the graph and know that you either forgot or incorrectly drew your line of best fit. Keep this document and refer to it often? I will also use a set of shorthand grading symbols when grading labs (homework, quizzes, and exams) This list may evolve as it gets used and refined, but here is what we will start with. Symbol Meaning ALG You have made an algebra error. CALC You have not included sample calculations for some part of the data table. DG There is a required diagram missing. DNF Does not follow. This statement of step does not logically follow from the previous one. DV Define the variables that you have introduced in this lab. FIND You have omitted or incorrectly specified what your are trying to find in the problem. FF Follow format. Follow the standard problem solving format outlined in the Problem Solving Format document, the Student Guide to Graphical Analysis, or this Lab Report Format document. GIVEN You have omitted or incorrectly specified the given information in the problem. GRID Make sure that your graph has a background grid. HOW It is unclear to me how you arrived at this. Show all steps necessary to reach the result you have shown. Explain your steps and/or reasoning in arriving at this result. HYP Your hypothesis is missing or incorrectly phrased. LABEL You have failed to correctly label the quantities in a data table, on a graph axis, or a diagram. COBF You have omitted or incorrectly drawn the curve of best fit for the graph. NT Not true. You have made a statement, either in English or mathematically which is not true. OE This is not an original equation. You should start any calculation with the original equation as approved in class and then show the algebraic steps necessary to yield the equation stated. PP Use point protectors for all data points. SC Support your Conclusions. See section 5, #18. SCALE Scaling is incorrectly done. Make sure that you have picked a reasonable scale, that it allows your graph to reasonable fill up the space, and that you have scaled consistently (equal increments) from zero on each axis. SE Use a straight edge to draw straight lines. SF You have used the wrong number of significant figures in your measurement or calculation. SL Substitute last. Perform the algebra on the equation to rearrange it to the form you need. As your final step, substitute in known values, including units. SS What is the significance of the slope of your graph. U Units are missing or incorrect. WHY Explain why what you have said is true. Fully support your statement or answer.