Day 36 – Working with Graphs

Physics 11 – We’ve started working with kinematic equations but before we got too deep into that, I had to go over graphing a bit more. Students really struggle with this topic. One reason for this could be that lots of the practice graphs I have them work with are really abstract in nature and don’t really describe any realistic motion.

It was time for Peer Instruction, and the above question and results were normal for the day. Vote #2 had a much higher correct answer rate.

Working with kinematic equations have brought forward two certainties in the physics classroom. Certainty #1 is shown below, and the question drives me crazy.


Certainty #2 is that students automatically go to equations to solve their problems.

I also saw people replacing variables in the work with an “x”. When asked about this, students said they are used to solving for x. So. Much. Work. To. Be. Done.

Day 62: Forces and Kinematics


Physics 11 – Students have been scaffolded into doing unbalanced forces with kinematics.  Students’ biggest hurdle seems to be thinking about what is being asked and drawing a force diagram.  I often tell my students that the force diagram is where all of the physics happens.  After that, most of the work is algebra.

It’s been over a month since the students were working with kinematics, and now equations reign supreme.  Not one student resorted to using graphical methods of solving the questions.  Not surprisingly I heard several cries of “I don’t know what equation to use.”  I have no solutions to solving this issue.  Clearly there are some deep habits formed somewhere, where the equation is raison d’étre.

Day 30: Problems with Graphs

kin4 q

Physics 11  Question and solution from last day’s quiz on constant acceleration.  The students were really starting to push back on the graphing.  One student spent the weekend with his tutor and had memorized d = vit + 1/2 a t^2.  He used it, although he wasn’t sure why it worked.  Another student had been researching the use of graphs, and explained to the class that at least 3 other high schools in our district used equations to solve problems.

My response that plugging numbers into formulas wasn’t much to aspire to, nor would it benefit them in university or in life.  Apparently tutors also disagreed with this, saying that they have degrees and used formulas in university.  Another student claimed that he just didn’t like graphing. Of course the real problem is that he still doesn’t properly understand how to construct and read a graph, which leads to him not liking them.

So that’s where we are.  Despite of the pushback, the lesson plan for the day was to use a v-t graph to develop some kinematic equations.  Developing the equations has dubious pedagogical reasoning behind it, but I like the idea of showing that the kinematic equations don’t automagically appear out of nothingness.  I’m ok with this rationale.

Oh, the above question… Very few students were able to recognize that the area under the v-t curve was displacement.  They had been practicing this concept but mostly qualitatively. Placing the graphs in the context of a word problem shifted their perspective. I had expected this, we were only into our 2nd day of dealing with word problems.