Day 62: Friction InvestigationsPosted: December 2, 2013
Today we started investigating friction. I was inspired to have students design their own experiments by John in this post, and I’m looking forward to comparing notes with him and Frank (see the comments of John’s post).
We started this process by going through the Friction Investigations page in my UBFPM packet here. The graph above was produced for #4. I was pretty happy with how this guided students towards the idea that static friction only acts as much as it has to (does anyone have a better way to say that, btw?), and that kinetic friction tends to be constant. After we finished up with listing then culling the possible variables to affect friction, I gave them some brief instructions on how to use the force detectors in this case and set them loose. I asked them to investigate qualitatively (if they were changing the speed, do a slow, medium, and fast trial), mostly because of lack of time.
I must admit I am conflicted here a bit because I am crunched for time to finish Unbalanced Forces before winter break. I know some groups are going to get the ‘wrong’ answer from their lab, and I would like to have all the groups follow up with either extensions or re-doing their lab (as Frank suggests in the comments), but I’m out of time. So unfortunately I think I’ll just demo the experiments (as I’ve done in the past) to show the “right” answer. But I hope I don’t have to and the data will speak for itself. We’ll see tomorrow.