Pat had alot of trouble with this experiment, recieving only 5 out of apossible 20 points for this experiment. The grading commentary below isorganized according to the Grading Breakdown given in the Experiment Notes. When grading a report, the TA should give feedback both on what was donecorrectly as well as what could use improvement. (Due to time constraints,though, these notes are much more detailed than those your TA will use. Pleaseask your TA for any necessary clarifications of their own grading notes.)
Pat misses the point here. The rings are being watched so that studentscan determine the mathematical relationship between the period of oscillation and the diameter of the oscillating ring. A good purpose statement gives boththe goal of the experiment and some indication as to how that goal is to bereached. Either one of these things alone would have resulted in a score of0.5 our of the possible 1 point.
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Pat doesn't really have a results section. A good results section shouldmatch the purpose of the experiment. In this case the goal of the experimentwas to study the graphs produced to determine a mathematical relationshipbetween two parameters. Because of problems with the graphs themselvse, Patwas unable to show which relationship was the correct one. Stating that thesethree graphs were unable to produce a linear relationship would have beenbetter than avoiding the issue altogether as Pat has done here. If you arehaving troubles deciding what to include in the results section, refer to theAnalysis Notes given on the Web Site for that experiment.
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Pat lost points for the calculations of the average period, of d2, and of sqrt(d). One of the points for the calculation section was assigned to the calculation of the average period. Pat never shows this calculation. It is OK for you to use the spreadsheetfunctions to do your calculations, but you should also give one exampleof each calculation including numbers. This is one very good way to check tomake sure you have entered the correct functions into the spreadsheet. Thesethree calculations are fairly simple, but it is best to get into the habit ofchecking the calculations for those times when the functions to be entered aremore complicated. Pat did recieve 0.5 points because he labeled the columns inthis table using the equations that were entered. If a sample calculation wouldhave been performed, Pat might have noticed that the computer calculatedd-1/2 rather than the correct d1/2. Correcting this would have resulted in a linear relationship for the T versus sqrt(d) graph as was obtained by both Mike and Maggie.
Two of the points for the calculations sections were for the linear fit ofthe graphs. One point would have been given for using a ruler to guesstimatethe best straight line through the data. A full 2 points would have been givenfor using linear regression to find the actual best fit line through the data.Pat received 0 points for this portion of the calculations because no best fitwas even attempted. The fact that no straight line was achieved should havealerted Pat to the possiblity of a calculation mistake somewhere.
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Pat did several things well in creating the graphs. Each data point on thegraph is clearly marked. Pat also chose good scales for each of the graphs sothat the data points fill the entire space rather than being shown in one smallsection of the graph.
Pat did make several mistakes, however, that resulted in lost points on theGraphs section of the report. Firstly, although the title of the first graphreads "T vs. d", Pat plotted the variables along the opposite axes. T should have been on the vertical axis and d on the horizontalaxis. This mistake was repeated on the other two graphs, losing Pat 1 point.Another half point was lost because the titles and axis labels were incomplete. Use words, not symbols in your graph titles and include the name, symbol, andunits of the appropriate parameters in your axis labels. Pat lost the lasthalf point for connecting the dots rather than drawing a smooth curve throughthe data points.
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In an analysis section it is important to explain what conclusionsyou have drawn from your results AND why you came to those conclusions. In a good English paper, quotes are used to support analysis of the text. In agood physics lab report, you should refer to your data, graphs, etc. to supportyour conclusions. Personal commentary about how well you liked an experimentis not necessary in a lab report.
The Analysis Notes asked students to discuss the shapes of teh three graphsand to explain how the shapes helped them determine the correct mathematicalrelationship between the period of oscillation and the diameter of theoscillating ring. The first two sentences of the analysis are actually validconclusions. Something has gone wrong and Pat has explained why it wasobvious that something was wrong. It was correct to think that theexperimental error could have affected the results, but Pat should also havethought to check the calculations as well. Pat recieved 2.5 out of a possible5 points for this portion of the Analysis Section.
If something goes wrong in one of your experiments, look at both thepossible measurement errors and at the calculations. If you still can't findwhere the problem lies, submit all of your attempts to find the problem. Explain in your analysis why you know something went wrong and document whatyou did to try to find the problem.
The Analysis Notes also asked students to discuss any experimental error intheir measurements. Pat merely says human error to cover anything that mighthave been done by any of the three lab partners. This is followed by a coupleof sentences maligning the equipment. Firstly, the words "human error" aloneare way too vague. Only use them if they are then followed by a more detailedanalysis of what exactly could have happened. For example, there might havebeen an error due to the reaction time between the person watching the ring andthe person running the computer's timer. Or there might have been a problem indetermining the exact center of the circle when measuring the diameter. Bespecific. Secondly, despite its age and use, all of the equipment used in thelab is sufficient to measure the appropriate data, providing that it is usedcorrectly. Pat received 0 points for this portion of the Analysis Section.