(version
Examples
of Lab Report Formats
A Short Introductory Note
While the previous document gives an overview of the physics lab report format and the approximate weighting of the various components within the report, applying these principles of lab report writing can best be illustrated by example. Your choice of format will be influenced greatly by the activities that you are asked to do for each lab. For instance some labs are focused on obtaining a single result, while other labs will lead you through a series of “mini-experiments” to build your understanding of the phenomenon in a step-wise manner. There is no “one-size fits all” lab report format that fits all of the cases. We will make some rather detailed suggestions for putting together the first few lab reports of the semester. After that you will be expected to make reasonable choices of format to convey in a clear and concise way the experiment(s) performed, the experimental results observed and calculations made, and the conclusions which can be made on the basis of your work.
A lab report does not need to read like a storybook. However, the reader of the report should not be expected to “read between the lines.” The reports, as we envision them, are more like logbooks documenting your lab activities with enough explanatory notes that a person, who did not attend the lab but has some minimal knowledge of physics, can read your report and can understand clearly the experiment that you did, the apparatus used, the data you took, the analysis of the data, and the significance of the results as stated in your conclusions.
The outline form shown below with Roman numerals, etc. is strictly an aid for clarifying the general organization of the report and should not appear as such in the finished lab report. However, you may wish to give headings (such as: Introduction, Data, Exercise 1, Summary, etc.) here and there in the report to guide the reader.
Suggested Format for “Motion along a Straight Line”
Lab
I. Exercise 1: Predictions for Cases 1-3
A. Make qualitative (no actual numbers) graphs of position, velocity, and acceleration as functions of time for the situation of the track and cart as described in Exercise 1, Case 1. Put all three of these graphs on one side of a single sheet of engineering paper. Make sure that the time scales on each of the three graphs are the same. [Note: Before making these graphs you need to think about where the computer will assume the zero of position to be and which direction is considered positive by the computer. You do have some control over the choices which the computer makes! Otherwise you may find rather wide discrepancies between your predictions and the actual graphs when displayed by the computer.] Use explanatory notes to aid the reader in understanding the reasoning behind your graphs. We do not expect your predictions to be 100% correct, after all that is why you are taking this class. Don’t be afraid to explain your reasoning even if it turns out to be incorrect. You can rectify the errors in your thinking when you see the actual results as determined with the help of the computer in sections II-IV below.
B. Do the same as in Sec. I-A for the track and cart configuration of Exercise 1, Case 2.
C. Do the same as in Sec. I-A for the track and cart configuration of Exercise 1, Case 3.
II. Exercise 2: Computer-generated Graphs for Exercise 1 (Cases 1-3)
A. Display position, velocity, and acceleration as functions of time in the same graph window using the Data Studio software. Having all three graphs together insures that the time scales for each of the graphs can easily be made exactly the same. Make sure that the linear motion calibration for the rotary motion sensor has been changed to correspond to “Large Pulley (Groove)” before taking the data. Rescale these graphs to show the regions of interest clearly BEFORE printing them out using the “landscape” print format to make them larger.
B. Obtain the computer data for Cases 1-3 of Exercise 1.
III. Exercise 3: Computer Graphs Compared Qualitatively with Previous Predictions
A. Qualitatively compare the computer-generated graphs to your predicted graphs for Exercise 1, Cases 1-3. Be critical and specific about any differences. Take time to explain any mistakes or ambiguities in your reasoning that led you to make an incorrect prediction or one that was not quite correct.
IV. Exercise 4: Analyzing the Computer Data Quantitatively
A. By definition the velocity at any given time equals the instantaneous slope of the position as a function of time graph at the same point in time. Likewise the acceleration equals the instantaneous slope of the velocity as a function of time graph at any given point in time.
B. Draw tangent lines by hand on the position as a function of time graph, compute the “slopes” of the tangents (make sure that these calculations are documented clearly and concisely in your report), and carefully plot these values of the slopes on the corresponding velocity-time graph at the correct time as determined by the point of tangency of the line on the position-time graph.
C. Draw tangent lines by hand on the velocity-time graph, compute the “slopes” of the tangents, and plot these values on the acceleration-time graph.
V. Exercise 5: Making a Quantitative Summary of Your Results
A. Compare the slope values from Sec. IV-B to the actual velocity values on the velocity-time graph with a table that also shows the percent difference given by [(velocity – “slope”)/velocity](100%) for each of the four times where you drew tangent lines in Case 1. Make sure that you illustrate your calculation technique for the percent differences by showing in detail at least one complete sample calculation. Repeat this procedure by making tables for Cases 2 and 3. It makes sense to include all of the data for Case 1 (both parts A and B of Sec. V) on the same table; however, the choice is yours.
B. Compare the slope values from Sec. IV-C to the actual acceleration values on the acceleration-time graph with a table similar to that discussed in Section V-A.
VI. Overall summary/conclusions for the lab
Suggested Format for “Free Fall” Lab
I. Make a diagram of the apparatus with annotations as necessary
II. Explain in detail how you configured the Data Studio software to get the necessary data for velocities and times.
III. Collecting the data with an empty film canister
A. Using Data Studio, collect the data for at least three “good” runs with the empty film canister. (A “good” run means that the canister passes through all four photogates with minimal twisting or rotating as it falls and without hitting a photogate.) You may need to assign one member of your lab group to observe the fall closely and to judge the validity of each run. The error due to twisting will be “one way” in the sense that a canister passing through a photogate with the axis of the cylinder rotated at some angle from horizontal will “appear to have” a larger diameter than one passing through the photogate with the cylinder axis horizontal. This will increase the time interval that the light beam of the photogate is blocked, thus artificially giving a smaller velocity than is really the case, because the computer is using the diameter you measured with the calipers to compute each of the velocities.
B. Demand consistent data. From the raw data given by Data Studio, collect and/or compute the velocities and times that you need for the velocity-time graph and put them in your own table so that you can verify the consistency of the values that will be used to make the velocity-time graph. If necessary adjust your experimental technique and take more data to get the consistency that you need.
C. Using the data from only the consistent runs, calculate the means and standard deviations for the velocities and the time intervals that will be used in plotting the velocity-time graph later. The standard deviations will allow you to calculate and plot horizontal and vertical error bars on your graph. Show representative calculations for all that you do here.
IV. Collecting the data with a canister filled with paper clips (but not so tightly that they don’t rattle a little bit).
A. See Sec. III.
V. Graphical analysis
A. Make two full page graphs (they can be combined if the legend distinguishes clearly between the two cases) of velocity as a function of time for the empty canister and the filled canister.
B. Use the standard deviations of the time intervals calculated earlier to give the horizontal error bars for each point and the standard deviations of the velocities to give the vertical error bars for each point.
C. Devise a method to get the accelerations from the velocity-time graphs.
D. Compare your experimental values of acceleration to the acceleration of gravity. Make a quantitative comparison. Do the values agree within the limits of uncertainty of your determination? A percentage error calculation is OK, but does not tell you whether the values agree within the limits of the uncertainty.
VI. Summary and conclusions