| Section # | Time | Teaching Assistant |
|---|---|---|
| 1 | Monday 12:30 - 14:50 | Chris Allmond |
| 2 | Monday 16:30 - 18:50 | Erick Crouse |
| 3 | Tuesday 15:30 - 17:50 | Erick Crouse |
| 4 | Wednesday 12:30 - 14:50 | Chris Allmond |
| 5 | Thursday 15:30 - 17:50 | Gwendolyn Smith |
| 6 | Friday 13:00 - 15:20 | Gwendolyn Smith |
| Lab # | Date | Experiment Title |
|---|---|---|
| 1 | 8/30 | Errors Analysis and Graphing |
| 2 | 9/6 | Curve Fitting and Model Analysis |
| 3 | 9/13 | Motion in One and Two Dimensions |
| 4 | 9/20 | Vectors |
| 5 | 9/27 | Newton's Second Law |
| 6 | 10/4 | Circular Motion |
| --- | 10/11 | Fall Break (sections 5 and 6 will meet for lab #3) |
| 7 | 10/18 | Conservation of Linear Momentum |
| 8 | 10/25 | Ballistic Pendulum |
| 9 | 11/1 | Conservation of Energy |
| 10 | 11/8 | Rotational Motion |
| 11 | 11/15 | Harmonic Motion |
| --- | 11/22 | Thanksgiving Break (yeah!) |
| 12 | 11/29 | Wave Motion, Doppler Effect |
For example, suppose you are trying to measure the heat loss of an object by recording a change in its temperature. After careful thinking about the physics of this experiment, you decide that you expect a temperature change no larger than 1.0° C. Based on this estimate, you conclude that you need to choose a thermometer that can accurately measure temperature in increments of 0.1° C or smaller. Also, you will need to make sure that no outside processes such as changes in the room temperature, holding the object in your hand, air conditioner blowing on the object, etc. will affect the temperature of the object during the measurement. If you have paid attention to all of these details, and have a rough idea of what to expect, you will be able to judge whether or not your measurement makes sense. If you are careless, don't pay attention to experimental details, and don't have any idea what result to expect, you would probably not be concerned if you measured a temperature change of 10° C, and would probably only discover the problem much later, when you begin to write your lab report.
The second skill necessary for good scientific research is really an outgrowth of the first skill presented above. When an experiment is finished, the usefulness of the results depend entirely on the uncertainty associated with the measurement. This means that you must constantly pay attention to details of the experiment and measuring apparatus that could give you erroneous results. It also means that you must accurately estimate these results when you present your final data. For example, if you are trying to measure the temperature of an object, and your thermometer seems to consistently fluctuate during any measurement by ± 2° C, you must include this error in your results. For example, you might say ``We measured a temperature of 33 ± 2° C.'' By paying attention to possible sources of error, and properly including these uncertainties in your final results, you give the reader a true sense of the significance of your results.
A good lab report will always have certain qualities which make it useful to outside readers. First, the report should be written in such a way that a non-expert (someone not in your lab class) could read it and learn what principles you were trying to test, how you did the measurement, what data you obtained, whether or not you confirmed the theoretical prediction, and what errors were associated with the measurement. Also, it goes without saying that the report needs to be readable, with complete sentences and proper grammar. A report with too little information will not be useful, and a report which is filled with unnecessary text and equations will often confuse the reader. Graphs need to be properly labeled and numbers should always be quoted with the appropriate units. Finally, the document needs to be readable. It is not a prerequisite that the report be typed, but handwritten reports are often messy and difficult to read. Word-processors such as Microsoft Word and Word Perfect have equation editors and work well for reports, and spreadsheet software such as Microsoft Excel do a great job at graphing and making concise tables of data.
To help guide you through your first lab report, here is an outline with suggestions for the type of information you might need to include in each section.
``In this experiment, we will attempt to confirm the ideal gas law which is written as PV=nRT. This law gives us a relationship between the pressure, volume, number of molecules, and temperature of a gas. The law will be tested by varying one quantity (such as temperature) and confirming that the changes in the other quantities (pressure, volume, and number of molecules) follow the behavior dictated by the ideal gas law.''
``In step one, we will fill a container of volume V with a known number of gas molecules n. We will then slowly heat the container while measuring the temperature and pressure of the gas. If the ideal gas law is obeyed, a graph of the pressure versus temperature should follow the equation P =(nR/V)T, with a slope of nR/V.''
``The plot of pressure versus temperature shown above has a slope of 10.1 Pascal/Kelvin. The expected value from the ideal gas law is 11.0 Pascal/Kelvin. Note that data point number three is very far from the rest of the points on the graph which might indicate a measurement error or problem with the apparatus...., etc.''This section is also the appropriate place to answer questions that are asked in the lab manual or additional questions that your TA might have for you.
``In this experiment we measured the relationship between pressure and temperature for a gas with a fixed volume and number of molecules. A plot of pressure versus temperature yielded a slope of 10.1 Pa/K and the ideal gas law predicts a value of 11.0 Pa/K. However, the pressure gauge was not stable and typically had an error of ± 20%. With this measurement error, our slope is 10.1 ± 2.0 Pa/K and is therefore consistent with the ideal gas law prediction.''
There is one final thing to remember about experimental science. You will not always get the ``right'' answer. This doesn't mean that your experiment was a failure. The important thing is to try and understand why things didn't work the way you expected. If you find that your measurement doesn't agree with the expected result, look for possible reasons. Perhaps the equipment you used was faulty or inaccurate, you missed a critical step in the procedure, or you simply recorded the data incorrectly or made a math mistake. Finally, don't forget that often in scientific research, the experiment doesn't agree with theory because the theory is wrong. Many important scientific discoveries would have never been made if scientists disregarded data that didn't seem to agree with a theoretical prediction.
To earn a successful grade for your lab each week requires that you successfully complete all steps of the experiment, write a lab report that presents the experiment, data, analysis, and error analysis in a clear and concise manner, and correctly answer all of the questions in the lab manual, and those presented by your TA. Additional creativity and useful input beyond what is asked for in the lab manual is encouraged, and will often earn you that extra point. Poorly executed experiments, poorly written reports (this includes the scientific quality as well as grammar and neatness), failure to clearly analyze experimental errors, incorrect answers to questions, unlabeled graphs, and unit-less numbers will cost you points. To summarize, a successful experimentalist is one who understands the scientific goals and principles behind the experiment, pays clear attention to the details and potential errors, and presents the results in a clear and accurate report.