One thing that is often hard to do in class is have full participation in a demonstration except for very simple demonstrations like blowing bubbles or the bendy straw momentum demonstration. It is also often hard to do more involved demonstrations due to a lack of time. One way around this is to have the students do the experiments themselves at home. I have recently started having take-home labs as part of my class (there is also a separate formal laboratory component to the course). The approach is very simple and I will post details about individual experiments later but wanted to post a bit of background and some reflections on my experience of the ups and downs of this approach.
Ben Sill used to do this a lot when he taught Introductory Fluid Mechanics in my Department. The basic approach is really simple.
- The students are given a task such as measuring the specific gravity of a couple of common fluids. I do not specify the fluids so they can use whatever they have at home
- The students are required to complete the task using at least two different techniques of their own choosing. No guidance is given on how to do the measurements.
- They are not allowed to use lab equipment except maybe a scale from our materials lab. Testing is to be done with what they can find around their home or can buy in a store for a few dollars.
- They are to write a brief report (3 page max) outlining their measurement techniques, analysis, and results. They also have to compare their results from the different measurements and discuss any differences. This includes quantitative error analysis for projects later in the semester.
The assignments are given in groups of 3 to 4 students. I give out 4-5 a semester and I give them about 2-3 weeks to complete the project.
- The students have to think for themselves about how to do the tests.
- They do research. I have had groups find research articles that they use in their measurements and analysis.
- They relate the project to their work in this and other courses. I have had groups use construction materials testing techniques and particle dynamics equations as part of their labs.
- They have to consider sources of error in their measurements and analysis. When they compare their two (or more) different values from their different tests they need to explain why they are different. For example, if you are trying to measure the exit velocity of water from a hose by filling a bucket then the result is very sensitive to your measurement of the hose diameter.
- They have to work in groups. I require that they provide a photo of themselves doing the tests so that everyone is seen to participate.
- They relate the analysis that they do in class to physical measurements using things they can find in the kitchen or buy at a grocery store.
- They can get very creative. I had a group measure their submerged weight by going to a local hotel pool and having someone stand on a scale at the pool edge holding a rope with another group member in the pool holding the other end of the rope.
- Some groups really struggle. They just have real difficulty working out how to do the tests and occasionally just end up lost and confused. I allow groups to self-select so I can get the odd group with a few too many weaker, less motivated, or less organized students.
- It is time consuming. Grading the reports takes time.
- The students typically get the measurements and analysis right but have trouble quantifying their errors and uncertainties. I plan to spend more time on that in class in the future.
- Some of the methods teams come up with don’t work because there is physics or fluid mechanics that they have not covered that means their analysis of their measurements is incorrect.
- There needs to be some rotation of topics so that students don’t just get ideas form previous semester’s students. I plan to use 4-5 per semester and plan on building a library of around 10 labs to rotate in and out. I will also need to tweak the report requirements to keep things fresh.
Over all I would say that my early experience with this has been positive. I plan on posting the instructions for each take home lab I use over the coming weeks along with some comments about how they did and did not work.
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 (firstname.lastname@example.org). I also welcome comments (through the comments section or via email) on improving the demonstrations.