Day 79 – Friction Inquiry

Physics 11 – Today was one of my favorite lessons for the year, where students propose things that affect friction and then carry out their own experiments to answer the question “what things affect the force of friction?”

This group’s work was pretty good, I especially like their force diagram. Yes, surface materials affect friction.

Here’s another group’s results. Check out the sweet bar graph.

One of the more surprising results: velocity does not affect friction. This group did a good job in carrying out an efficient test. They knew that they didn’t have to measure velocity, they only needed to use two buggies that clearly had different velocities. They also were clear that what they really had to measure was force.

Two groups working on surface area had different hypothesis. The above group is the first time that I’ve had a student predict that surface area would not affect friction, and he managed to convince his group of this prior to them carrying out their test. That was pretty cool.

Mass affects friction. I drew points on their bar graph to emphasize what looks to be a linear relationship. I had encouraged them to do an x-y graph but they went with a bar graph.

One thing that I noticed a few times was groups being confused on what to measure.  It’s possible that only 1/2 of the students were able to design the experiment while the other half listened and were convinced by their peers on what to do.

One group was supposed to see if velocity affected friction and they concluded that it did. However, we noticed that they only tested one velocity.  Other groups were correctly dealing with their experimental variable, but were measuring time or distance instead of force. I will spend a day working through Smarter Science with them…

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