Physics 111 Lab: Area of Table Top

The goals of this exercise are the following:

  1. Start thinking about the most accurate and precise ways of measuring something.
  2. Learn how to calculate uncertainties the quick and easy way and gain experience doing so.
  3. Write a good lab report.

Many of you will go off into careers where you will often be required to measure something and report back the result to your boss and/or other co-workers. This lab will introduce you to doing something very similar. Granted, the area of a table top has very little to do with Physics 111, but at least the goal is easy enough so that you can concentrate mostly on writing a good lab report and calculating uncertainty correctly.

So pretend I’m your boss. I want to know the top surface area of your table top (the black part). Here is specifically what you will do:

  1. You will work with your tablemates (groups of no more than 4). Determine the most precise and accurate way of measuring the dimensions of the table top.
  2. The longer dimension must be measured three times by each person in your group. The value you use for this dimension will be the average of these measurements, and the uncertainty will be the standard deviation in these measurements.
  3. The shorter dimension must be measured only once, with the uncertainty estimated.
  4. Each one of you will write a report explaining your result and how you got it. I would prefer that this report were handwritten, and I encourage you to write it up as you do the experiment to save time. It will be due no earlier than the start of the next class period. The format of these reports will be as follows:

Name/Partners/Date/Title (0.8 points) – At the top, write your name, the name(s) of your partner(s), the date you did the experiment, and give the report a title that has something to do with the experiment.

Introduction (0.4 points) – This section states the goal of the experiment. Most of the time, this need only be one sentence long.

Theory (1.0 points) – Here, you derive an equation that relates the quantity that you are ultimately trying to determine with quantities you wish to measure. For example, if you wish to measure the acceleration of gravity, you would derive the equation g = ½ a t2 (or something like that). For this lab, there is no need to derive the equation area = l w, but you must state this formula and define what each term represents (w = width or shorter dimension, etc.). (If you come up with a better way to measure the area using a different formula, you may need to derive the equation that goes with your new method.)

Experiment (4.0 points) – In this section you describe how your data was taken. This must include a diagram and equipment numbers (or brand/model if no equipment number is available). You must include enough information here that 10 years from now, long after you or I have forgotten this experiment, someone else can duplicate your experiment using the same method and equipment. If you are not sure if you should write it down, write it down anyway! You need to especially include little things you did to make your measurements easier, more accurate, or more precise. ALL OF YOUR DATA GOES IN THIS SECTION. Also, THIS SECTION MUST ALSO INCLUDE A DIAGRAM.

Analysis (2.0 points) – Here is where you crunch your numbers. For this lab, you will show your calculation for the area of the table, and the calculations for the uncertainty in the area of the table.

Discussion (1.0 points) – In this section, talk about your result. Is it reasonable? Does it agree with other measurements? Why or why not? In this lab, we have no manual for these tables that specifies the area of the tabletops, but you may compare your result with other groups in the class.

Conclusion (0.8 points) – State your end result (with uncertainty). If it agrees with other measurements or theory, say so. If it does not agree with other measurements or theory, state what was wrong with the other measurements or theory. IF YOU MADE A MISTAKE WITH YOUR MEASUREMENTS, GO BACK AND REPEAT THEM. Do not turn in a lab report where you knowingly made a mistake! Also, nothing new should be said in the conclusion. It should just sum up your main result and the conclusion of your discussion section. The conclusion should be at the very end of your report, and be no longer than a couple of sentences.

The lab report should be organized, but if there are things crossed out or erased, that is ok. The conclusion should come at the very end. If I (your “boss”) don’t have time right away to read the whole thing, I want to be able to find the end result without having to look for it. The first place I’ll look is at the very end.

Spelling and grammar do not matter unless I cannot tell what you are trying to communicate.

Richard A. Thomas – UST Physics