Over the past two weeks I’ve been doing a lot of new things, and I want to get them down:
#1 Hover pucks
Not only using hover pucks, but revisiting them again and again. We began forces by taking hover pucks out into the hallway and observing, describing in words, and drawing velocity vs. time graphs for
- Motion after pucks were tapped fairly hard and very hard
- Motion of puck while being tapped once every second
- Motion of puck while being steadily pushed
We visited the pucks again before vectors and projectile motion. We sent them going down one hallway, and when they got to the second hallway, we tapped them in the other direction. Students made predictions and observations, once again using words, but this with pictures showing the trajectory,
We visited hover pucks again when making a bridge from projectile motion to circular motion. How to get the hover puck to move in a circle by tapping?
Beyond just “using” hover pucks”, hover pucks became an anchoring context for conversation again and again. Oh, I almost forgot, before the first time we used hover pucks, students took one of the formative assessment activities from Paige Keeley’s book, “Uncovering student ideas in physical science.” It was the one where there is a list of a dozen or so statement about force and motion that students have to agree or disagree to. I had students commit to answers before, and then revisit after. As a class, we talked about a few sticky ones.
#2 Velocity vs. Time Graphs
This summer, velocity vs. time graphs are the major tool we use all the time. As others have said, velocity vs. time graphs are rich with information. The great thing about velocity vs. time graphs is that you never stop using them.
I think that the first activity with the hover pucks was only successful because we had spent a lot of time the week before working with velocity vs. time graphs. Students worked problems using them. My exams required students to interpret them and draw them. I asked clicker questions using them, both before and after hover pucks, and all the time. Questions included quantitative ones, qualitative ones, and questions that went back and forth between considering position vs time and velocity vs. time.
One last note about velocity vs. time graphs. This summer, on any problem involving forces, I have not once given students acceleration or asked them to solve for it. If they need acceleration, they need to get it from a velocity vs. time graph or from a table with data. If I am asking a question about motion, it is about how much the object’s speed will change in a given time, or how much time it will take to go from one speed to another.
#3 Positioning Students as Authors of Ideas and Equations
To a degree, I have always done this. The first semester I taught here, a student named Ashley proposed the tentative idea that when you throw a ball up with a certain speed, it will hit your hand with the same speed. That idea became known as Ashley’s idea, which students used throughout the year to solve problems via symmetry. This year, a student proposed the idea that finding the velocity of an object is the same as finding the slope on a position vs. time graph. That rule is known in our class as Chelsea’s Rule. We also have a Yalda’s rule. etc.
What I am doing differently this year is framing Newton’s 2nd law as an activity of inventing equations. See in kinematics, the equations are pretty much always the same, but with forces, the variety of equations you can write increases a lot. AND, a single equation can describe different situations.
Typically, when we are working on force problems, my instructions are:
- Draw an interaction diagram
- Draw a free-body diagram (or more) for the object or system you think is important
- Invent an equation or two that describes the relationship between those interactions
In the past, students have had a really hard time when we start writing lots of equations without any numbers. While it is still hard and intimidating, it is much easier this year than before. I think some of this is because I am positioning students as inventors of those equations; rather than their being a right equation that was known ahead of time, which they were merely supposed to recreate.
Tied with this, we have been doing lots of Alan Van Heuvelen’s Jeopardy questions. I’ll write an equation like this on the board
T – (150 kg) (10 N/ kg) = (150kg) (-2 m/s/s)
and students will have to draw the free-body diagram and describe the situation. While there is only one free-body diagram really, there are multiple situations, because the -2 m/s/s doesn’t tell us direction its traveling or whether it’s slowing down or speeding up, so there’s a rich conversation to be had.
I think the Jeopardy questions pair well with the idea of inventing equations that describe situation, and positioning students as authors of equations. Another big thing to note is that forces isn’t the first time we did Jeopardy equations. I introduced them during kinematics as equal, and we practiced them with projectile motion. I even have exams questions with them.
#4 Leveraging History of Physics and Contemporary Physics
This paper by David Brookes and Eugenia Etkina has changed the way I think about thinking about force, learning force, and teaching force. It’s changed my thinking in a lot of ways, but one influence it has had is in helping me talk about students’ difficulties learning through the lens of history. This may sound crazy, but I explicitly talk with students about the words force impressa and force viva. I talk about this on the very first day after we’ve done the formative assessment and hover puck activity, and students are revisiting their initial ideas.
In talking about current days physics, I am doing a better job of framing the work we are doing in terms of current research. This is a perhaps a contrived example, but I think it still helps. We do this lab–one that I don’t like all that much–where students use uniform circular motion data to determine the mass of a ball. I frame this lab as involving the same set of ideas that astronomers use to study dark matter and in finding planets. (OK, it’s not exactly the same, but close). We talk just a little about how we measured the period of the ball going around, and how Astronomers measure the period of planet going around a star very far away. I didn’t make a whole lecture of it, and I wasn’t trying to sell the lab as something cool. It’s just a little thing that helps put our class in contact with larger participation in physics.
I also explicitly talk about the history of physics with Galileo. I spent the early part of the summer reading all of Galileo’s Two new Sciences. We talked about Galileo’s definition of uniform motion and why he changed it. We examine data and try to make sense of what Galileo meant when he said falling objects follow the odd number sequence. The more I know about the history, the better I find myself able to teach that physics.
#5 Working “problems” with data gathered in class, rather than contrived made-up stuff
Instead of working on some circular motion problem that I thought up, we get a buggy going in a circle with a string. We try to figure out how much tension is in the rope, and students help decide what data to take and help take data. I even have more than one students do the timing and the distance measurement, so we can do uncertainties if we want. I’m doing a good job of doing this quickly, and not dragging it out and making it a lab. It’s just a problem. Sometimes, we’ll try to verify our answer by taking more data; but I don’t have to if we are pressed for time.
#6 At-home experiments and in-class everyday object labs
I’ve had students share experiments with family and friends (dropping paper and book). I’ve had students make predictions and make observations (running key drop) at home. I’ve had students grab everyday objects and share observations and thoughts online (one where students had to get two pairs of shoes and describe what they notice about each that’s informing their decision about which has better traction). In class, students brought their shoes, and we did a lab to calculate the coefficient of friction between shoes and the floor.. I think I got this from Frank Noschese, but can’t find a link.
I have a goal, which is to help break down the walls between my class and the rest of their lives. I do this by asking them to share their learning with others, and to bring those others’ ideas back to class. I ask students to bring stuff to class into do experiments on. I ask them to do experiments at home. Maybe, just maybe, it will make a small dent.
#7 Bridging Analogies:
This year I did two of the bridging analogies described in this paper by John Clement. We did the Normal Force one and the Friction one. Because of time, one of these was done more teacher-centered than I would have liked.
#8 PhET Simulations
Right now, I am mostly PhET simulations using these for “lecturing”. I used moving man to introduce the number line as the system we are adopting for describing linear motion. I also used the vectors simulation for formalizing our observations in the hallway (with tapping hover puck in orthogonal directions).
I imagine I could get students more involved in the future, but for right now this is how I am making use of the simulations.
#9 Online Videos from Veritasium
There are multiple reasons for this, but one is to supplement our text, but another is to learn through refutation text (or video).
#10 Mindset Conversations
So far this year, we have talked a lot about learning how to learn. I have been most encouraged by John Burk to make this an important part of my class. A comment here describe a bit of what I have done so far.
Oh, and of course, my last post, about interaction diagrams.
** When I read all of this, I have think to myself, “How in the world did we do all of this happen in two weeks?” I have no idea…
Oh, right, and don’t forget about standards-based grading!