It’s a Physics World After All

LAB OBJECTIVE
Laboratory experiments will teach you how to investigate physical phenomena scientifically. This involves taking accurate data, analyzing that data, and inferring conclusions from your results. These skills will be applicable to other technical fields while in high school, college or beyond.
Lab write-ups will generally be collected the Monday following the experiment. When I collect lab write-ups, I may only collect one from each group. Group size may vary from two to four members. You will decide as a group whose lab will be turned in. However, everyone must have a complete lab write-up and they will be stamped on the due date. If you do not have your lab completed on time, or you are absent the day the lab is due, you will turn in your lab individually once it’s completed and not receive the group grade. Your grade will be reduced 10% per day late (excused absences excluded if lab is turned in the day you return to class).
Lab make-ups will occur only twice during the grading period and will be at my discretion. This will typically occur during the lunch period. If you are not physically present for a lab, you may not get the data from another student in the class to complete the lab. In other words, to get any credit for a lab you must be present for it execution. With that said, you get no credit for just showing up for the lab. You must turn in something to get any credit for being there.
You will work in groups of various sizes for the different labs. However, your write-ups should be written entirely by yourself. I encourage you to discuss the lab, problems you might have had, and sources of error.
Much of the lab equipment has been recently purchased while some are many years old. Because the cost of this equipment is high, even though they may not look fancy, treat them carefully and put them back where you found it so as to ensure that it may last many more years.
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LAB REPORT
Lab reports could take the form of one of the following:
1.
A simple write-up in which the objective, materials, procedures are usually provided and you conduct the experiment, collect the data, analyze the data, and answer basic questions provided.
2.
A formal write-up where you design a lab activity based on a concept covered. Here only the objective, planning, variables, and materials needed, will be written up. No actual experiment or data will be collected.
3.
A formal lab write-up in which you have designed most of the experiment with little, if any information, provided by the teacher. You will need to follow all of the guidelines below, use the sample lay-out provided and completely type your reports. Attach handwritten data, drawings etc. to your formal report.
I. TITLE AND FORMATING
1.
Make the title meaningful (eg: “Lab Experiment” is not an acceptable title but “Measuring the Simple Harmonic Motion of a Pendulum” is.
2.
Include the lab number in the title (eg: LAB 11-2)
3.
In the right corner of the first page put your name followed by your partner(s) name(s). The period of your class, and the date the lab was conducted.
4.
Every page following the first one needs your name, date lab was conducted, and page number in the upper right corner.
II. PROBLEM/QUESTION or AIM
1.
Define the problem and write it as a general statement.
2.
The question is very specific and written so that the answer may be found through a controlled experiment.
III. HYPOTHESIS
1.
Not all experiments will need a hypothesis. If the lab is about learning a particular piece of equipment, then a hypothesis is not appropriate.
2.
When a hypothesis is required relate it directly to the research question.
3.
You need to make a prediction.
i.
Bad Example: The pressure and volume of a gas are inversely related.
ii.
Good Example: For a fixed amount of gas kept at constant temperature its pressure is inversely proportional to its volume.
4.
Explain the hypothesis, at a fundamental level and quantitatively where appropriate.
IV. VARIABLES
You will be conducting experiments to search for cause and effect relationships. The experiment will be designed so that changes to one item cause something else to vary in a predictable way. These changing quantities are called variables. A variable is any factor, trait, or condition that can exist in
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differing amounts or types. An experiment usually has three kinds of variables: independent, dependent, and controlled. The independent variable is the one that is changed by the experimenter. To ensure a fair test, a good experiment has only one independent variable. As the independent variable is changed you will observe what happens. You will focus your observations on the dependent variable to see how it responds to the change made to the independent variable. The new value of the dependent variable is caused by and depends on the value of the independent variable.
For example: If you open a valve to a water pipe (the independent variable), the flow rate (dependent variable) changes. The number of dependent variables in an experiment varies, but there is often more than one.
1.
Identify the manipulated variable (independent).
2.
Identify measured variable (dependent) and how it will be measured – include both quantitative and qualitative variables.
3.
Identify variables that will be held constant.
Example: the size of the valve opening afore mentioned.
V. MATERIALS
1. Include all materials used (size, volume, mass, etc.), and the quantity.
2. Describe any equipment/instrumentation used (ticker tape machine, voltmeter etc.).
3. Do not list equipment from a lab sheet if you did not use them.
VI. PROCEDURES
1.
Include a picture of your lab set-up (hand drawn neatly or photo).
2.
Your procedure should not be just a list of steps. You should also include an explanation of how you control the variables and list the calculations/data manipulations that will be done so that you are sure you’re collecting enough data.
i.
The question to ask yourself is: Could someone who had never done this experiment before, reproduce exactly what you did in the lab with the instructions written?
ii.
Specifically states when and how (units, with what instrument) each variable is measured.
3.
Control of variables. This may seem redundant if you’ve listed variables in the variable section (IB only) but you need to explain your choices and how you will control the control variables here.
4.
List all of the possible errors that could occur and then explain how you will address them.
5.
Write down any assumptions you are making.
6.
Describe what measurements will be taken so that when data is processed there is sufficient data.
i.
List the equations you will be using and stat how each variable will be measured.
ii.
Insufficient data may be graphed but there may only be two or three points over a small range.
VII. DATA COLLECTION
1.
All data collected with units, significant figures and uncertainties
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i.
Record all raw data with precision and presented in an organized way. (Do not assume that someone will look in the procedures to find out what mass length rope was used. Record that here too.
ii.
Every time you make a measurement – write that number down even if it’s the same each time.
iii.
Include constants and givens
2.
Organize all data and presentation
i.
Data is in tables and tables have unambiguous titles and numbers.
ii.
Organization is logical, allows for easy interpretation.
Example: Table 1: Resistance of a conductor versus its length.
LENGTH
(m)
POTENTIAL DIFFERENCE
(V)
CURRENT
(A)
RESISTANCE
(R)
0.20
0.630
0.190
3.315
0.40
0.992
0.150
6.613
0.60
1.002
0.101
9.921
0.80
1.090
0.082
13.21
1.00
1.215
0.073
16.70
VIII. DATA ANALYSIS
1.
Show all calculations and graphs in their proper format
2.
Results are clearly presented in tables and graphs with units and uncertainties.
3.
Calculate averages, lines of best fit and look for other ways to graph data to get more information.
4.
All calculations must be clearly laid out. Show the equations used and unit analysis. Footnote calculated data shown in data tables with the sample calculations. You should do them on scratch paper first and then copy them into your lab report.
5.
Briefly head each calculation with what is being solved for.
IX. CONCLUSION
1.
Summarize what was done – restate the purpose of the experiment.
2.
Interpret your results and draw a conclusion
i.
Describe and explain the theory behind your calculations that were performed on the data.
ii.
Give reasonable alternative explanations for the results.
iii.
Look for any patterns you can find: look for upward trends/downward trends etc.
3.
State whether your hypothesis was supported or not.
4.
Compare to literature values and provide % error where appropriate (if there is no literature value than be sure to discuss the applicable concept/theory).
5.
Leave detailed analysis of error out of this paragraph and focus more on what your results do tell you rather than on why they might not be valid.
6.
Error analysis
i.
Identification of Errors
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a)
Leave out human error, miscalculations, time allotted, lameness o lab partner(s), etc. Focus on the errors in the lab procedure, equipment, and management of time. (If you state that the stopwatch was not accurate – show proof!)
b)
What are the limitations, weakness or errors in your procedures?
c)
Are there things that came up that you didn’t account for?
d)
Id you forget to calibrate the equipment, or set it up incorrectly?
e)
Is your technique poor, causing large random errors?
ii.
Effect of Errors
a)
Was your value too low? What errors contributed to making it low?
b)
Was your value too high? What errors contributed to making it too high?
c)
Which error, of those listed, was the most insignificant?
d)
Are your results reliable, given the errors listed? Justify this.
e)
Estimate the magnitude of errors if possible.
X. ENVIRONMENTAL
You will be assessed on the following, even though it is not specifically part of your write-up.
1.
All safety rules were adhered to.
2.
You and all members of your group remained focused on the task at hand.
3.
All instructions were followed accurately.
4.
All equipment were treated with care and returned exactly the way they were found.
5.
Any equipment damaged during the lab was reported to the instructor.
6.
If any, of afore mentioned situations are not adhered to, and the instructor is not able to determine which group violated protocol (equipment breakage, not returning equipment to the proper location etc.) will result in the entire class being penalized).
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LAB NOTEBOOK
Your physics lab notebook must be kept in a 3-ring binder. Do not use a spiral notebook or stuff your labs into a pocket folder. Set-up your lab notebook as follows:
•
Title Page Your name Period
•
Table of Contents Experiments name – Left side Lab Number (i.e. LAB 2-1) – Middle Date conducted – Right side
•
Labs in the order performed
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Other Type all labs Put a single line through mistakes instead of emptying your ink pen crossing it out. NO WHITE-OUT. Keep each lab organized and in a logical order (e.g. don’t put materials and procedure after analysis). Every page for each lab needs a name, date and page number. Attach all handwritten data to your formal report. Attach all simulations to your report. Write your labs in the 3rd person rather than the 1st person. Example: “The ticker tape readings were incorrectly recorded.” Is preferred to “Isaac was a klutz and read the ticker tape wrong.” Every lab requires a diagram or picture of the set-up. This is part of your procedure.