Physics 11 – Students presented their results on whiteboards today. In one class it is like pulling teeth to get students to talk in a whiteboard meeting. It is incredibly frustrating. I spoke with a few students after class, and they thought that maybe 1/2 the class was actually able to answer or question things that were said during the meeting, but chose not to.
Students did a good job of determining that the slope of the line on a Fs vs x graph is the stiffness of the spring, so that was pretty cool. Many groups didn’t think to find the equation of the line which was another beat my head against the wall moment. I really would like to get a modeling workshop here in Vancouver so I can improve on this aspect in my classes. Students are slowly coming around to the idea of modeling physics, but other details like having the kids take over discussions in class, along with timing on topics, continue to elude me.
Physics 11 – Today was the students’ first shot at whiteboarding models that they’ve developed. The photo above is interesting because during their presentation, this group realized that the direction on their graph was wrong.
The group below has a valuable statement on possible errors in data:
And the group below were the only ones that got to point of getting a mathematical model of the buggy motion. They had some good things to say with their presentation, more than what is shown here.
Physics 11 – Today the students had their first buggy challenge. I asked them to use their graphs from their CV Buggy lab to develop a strategy for predicting where the fast and slow buggy will collide if they’re given a time. A few groups got the idea right away, while some groups really wanted to calculate something. Overall the students came up with good, workable ideas.
After completing their challenge, students continued along with some modeling worksheets.
Physics 11 – The day started with a ball drop activity before we moved on to using constant velocity buggies* to analyze motion and come up with a model for constant velocity. To reinforce how “almost meaningless” the physics in Science 10 is (they do kinematics in science 10), most students perform this task as if they’ve never studied motion before. This suits me fine, because we get to start from scratch with model building.
I got the “it depends” idea from Brian Frank and his excellent blog: https://teachbrianteach.wordpress.com/2015/08/26/day-3-launching-the-buggy-lab/
I also reviewed how to get an equation of a line using the slope-intercept form. I anticipate many battles over the next few weeks as kids are weened off of x and y, and start to view symbols as having a meaning and not just a placeholder for something that is solved for.
* My choice was either to use $220 of my $250 classroom budget for the year and buy the buggies through the school and their supplier, or spend $100 of my own money and order the buggies myself (from the USA for less than 1/2 the price than the rip-off educational science stores). I bought them myself. That’s what we have to do in BC.
Physics 11 – Today the classes did the main modeling lab for unbalanced forces and Newton’s Second Law. I’ve used the modified atwood lab in the past, but wasn’t satisfied with it due to friction and hand-waving with transferring mass from cart to hanging mass. I also tried to setup an atwood apparatus as described by Josh Gates. In this setup, you hang a mass from one side of the pulley, and on the other side you hang another mass via a force sensor. If you time how long it takes for the force sensor to travel a certain distance, you can calculate its acceleration. You get the Fnet directly from the force sensor. I also found this lab setup to be difficult, particularly because it really works best with a wireless force sensor. In the end I opted to have the students get data directly from a force and motion simulation.
Prior to starting the lab, we qualitatively discussed unbalanced forces via Peer Instruction. I did this instead of the suggested modeling lab with qualitatively measurement of pulling a person on a cart. PI afforded some good discussion and I’m relatively confident that students understood the idea of unbalanced forces causing an acceleration.
Physics 11 Today we finally graphed data from our constant acceleration lab. There were several hurdles to overcome, most notably the kids getting their head around what a tangent line is. We finally had some really good discussion with the whiteboards, with students really challenging each other.
Some common pre-conceptions encountered:
- the velocity time graph should have horizontal lines (like before)
- points on the graph should be connected with a line
- a faster starting push on the object should make the v-t graph steeper because it’s going faster
I’m not sure yet how I will deal with the quadratic relationship. If I go over curve straightening, it will certainly be a bit hand-wavy.
We got to use our textbooks again today. Not only that but we also managed to incorporate the use of some biology books. Physics truly is the underlying science.
The students managed to collect what looked like decent data and plot their x vs t graphs. Next day I will have them find tangents and create a V vs t graph. I suppose we’ll even try some curve straightening to develop a relationship between position and time.