Take home lab – Personal specific gravity

This is a fun take home lab as the students have to measure themselves. It is also a lab in which the student should know roughly the answer before they start. Generally speaking, most people either just float or just don’t and therefore their specific gravity should be approximately S.G.=1. As with all the take home labs the students are required to use more than one method. The fundamental problem is measuring a person’s volume. There are a range of methods for doing this which often have significant uncertainty/error. There is, therefore, the possibility of having significantly different values from the two different measurements that must be reconciled through the error analysis.

When giving this as a take home lab I have generally found that the students are able to find two, and sometimes more, ways of doing the measurements. The students also sometimes borrow methods they learned about in other classes such as their materials lab. Once a team even worked out how to measure their submerged weight. It is a nice introductory take home lab as the measurements are easy to make but have significant uncertainty. Therefore, it is a good platform for discussing error analysis before they get into the more complex take home labs to follow.

As with all the take home labs I will not publish detailed methods for conducting the tests as I still use them in class and want my students to figure it out on their own.


Instructions to students

Introduction

The specific gravity of a fluid is its density divided by the density of water. But specific gravity is not unique to fluids. Your goal is to calculate the specific gravity of one of your team members using at least 2 different approaches.

Task

  1. Run a series of experiments to establish the specific gravity of either a member of your team or the team as a whole (or both if one particular method suits an individual test and the other suits a group test).
  2. Write a brief report that
    • Is 3 pages max including photos of you running your experiments.
    • Describes the experiment(s) you used to establish your result including:
      1. How the test was run.
      2. What data you collected.
      3. How you performed your calculations including diagrams, equations, and relevant theory that has been covered in in this class.
      4. A quantitative discussion of the uncertainties in your measurements and calculations including an analysis of the differences between your two sets of measurements.

Due in 2 weeks


An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.

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