In my Physics 10 update/upgrades, I built a new paradigm investigation for the Constant Acceleration Particle Model. The activity described here gets at the same things as my older activity, but it allows groups to do the investigation rather than the entire class together, and it gives more structure and space to the discussion. The students do more of the talking (and more of the students do talk) in this version, too.
Before this model, we have done Constant Velocity, Balanced Forces, and an introduction to Center of Mass.
In my Balanced Forces unit, students have practice thinking about and drawing qualitative velocity-time graphs when objects are speeding up and slowing down, so they have been primed for this work and discussion already.
Fan Carts and Motion Sensors
This activity starts off the unit. Students have already seen fan carts, so the “Hey, I want to show you something (relatively) cool” moment is to show them the motion detector.
We gather around a lab table. I have a student bring up their computer and set up Logger Pro. I show them the motion detector. Get everyone to be quiet enough to hear it click when we turn it on. We get to talk for a moment about what it is doing, then I show them how it makes the position-time graph. We move the cart back and forth in front of the sensor to get our bearings with how it all comes together.
I had out the packets, and they open them to the first inside page—the fan cart investigation.
At this point, they are set to do the first part of the page in groups, but it saves some time to have them talk for a minute about how to get a fan cart to slow down. At this point in the year, a lot of them still have a strong idea (whether they realize it or not) that everything starts from rest, so it isn’t very obvious to them how you could get one to be slowing down. A frequent suggestion is to “put your hand in front of it”. It only takes a moment to show them that if the cart is already moving, the fan can slow it down (depending on the direction it is facing).
Although the page only asks them to do slowing down once, since it doesn’t specify the direction, both directions will usually show up in the work among the different groups. That little bit of ambiguity adds to the discussion, and helps students focus (during the discussion) on the difference between how the velocity-time graph shows the direction of motion and how it shows speeding up versus slowing down.
The groups spread out and work through the three situations. Learning to use the motion sensors well takes a little coaching from me. As I move around to different groups, I help them identify which part of the graph shows the motion they wanted to capture and encourage them to sketch only that part on their papers.
Board Meeting and Discussion
After capturing graphs for the three situations, groups make whiteboards of the top portion of the page.
Once they have put the graphs on the boards, the class circles up for a board meeting. The first order of business is to come to an agreement on what the graphs looked like. They move to translate the bits of messiness from the real graphs into simpler shapes that show the essence of what they captured. Their goal is to come to a consensus about the 6 graphs. As they listen to questions and comments from their peers, they update their boards to show their thinking. Sometimes they look back at their computers to check a graph. It’s easy enough to quickly run one again if we are having trouble coming to agreement. Was the line straight or was it a curve? Which way did the curve go? Were you drawing the graph just for when the cart was speeding up, or did you also draw the part when your hand stopped it? It takes a few minutes to get all of the whiteboards updated, but they can handle that discussion mostly on their own.
The next phase of their discussion is centered around the questions at the bottom of the page (as well as in the top right-hand corner of the page). Their new goal is to come to a consensus about what information about an object’s motion they can learn from a velocity-time graph. In this part, they are able to lead most of the discussion themselves, but I throw questions into the mix, too. By the end, they are in agreement about how to tell the direction of motion, whether an object is speeding up or slowing down, and what the graph looks like when the object is changing directions.
The last step is to see what we can say so far about the slope of the velocity-time graph. What would it mean if the graph were steeper? That part is easier—and we come to agreement pretty quickly that a steeper graph could mean, for example, that the object is speeding up more quickly (maybe the fan is set to a higher setting). The tough part is—what does the sign of the slope mean? They talk about it a bit, but come to realize that they aren’t quite sure what it means. Not yet. I don’t let them get stuck in this discussion for too long. We set that part of the question aside as something we can investigate later. This is only page 2 of a brand new packet, after all.
Finally, I ask them if they’d like to know the name that physicists give to the slope on the velocity-time graph. We define acceleration as the slope on the velocity-time graph—a definition that will be a helpful way of thinking about acceleration for some time to come.
The next day, we follow up on our ideas about the shapes of these graphs and the meanings of the features by doing a Walk-A-Graph activity where students practice being the object for a variety of x-t and v-t graphs.
This model-building class activity fits well with Modeling Instruction pedagogy, and it is shared under a free and open copyright. Please feel free to use, modify, share, etc—as long as you follow the Creative Commons license on this page. Let me know if you try this with your students!
One might think that this would be more challenging (or even impossible) to do since these stations need to involve objects with changing velocities (so the handy flip-up index cards wouldn’t work for checking answers). Challenge accepted (and accomplished, I think).
Since this was our 4th unit, students were already comfortable using the force and motion sensors, so these tools could easily be used at stations without much or any additional instruction.
This course is an untracked 10th grade physics class with students in different levels of math, so I limited my first set of stations to situations with only horizontal and vertical forces to keep the focus on the physics concepts and not bury the point with more complex math. By the time we were finishing the unbalanced forces unit, a few weeks later, we had already been working force problems with angles in them, too.
Descriptions of the Stations
Balanced Forces with Angles
The only balanced force station, this one has a known mass of 410 grams and instructions to pull horizontally with a spring scale so that it reads 3 N.
The numbers chosen work out to make a 3 N – 4 N – 5 N right triangle in the force vector addition diagram. I hoped that by choosing those numbers (and no set of numbers screams triangle to high school students more than 3, 4, 5) it would help reinforce the idea of adding the forces as vectors.
Fan Cart Acceleration
Students use a force sensor (a push-pull spring scale would also work) to measure Fn(air) on the cart. Then they predict the acceleration of the cart. They check their answer with a motion detector.
In these photos, I have a setup that includes materials that are (frustratingly) no longer sold by PASCO, but any fan cart setup would work for this station.
For some of these stations, including this one, I included information about the mass of the object so that I wouldn’t cause a traffic jam or use up time with each group needing to use a balance to find masses at each station.
Pushing a Box
Students push an object with a push-pull spring scale or a force sensor. They are supposed to push with a constant force and make sure the object speeds up. Then they determine the friction force that the object experienced. Finally, they check their prediction by pushing the object so it moves with a constant velocity and measuring their pushing force.
This station turned out to be the “aha!” moment station of this set of problems. It’s a bit tricky to implement, so I spent the most time hanging around this station to help various groups get going with pushing the box correctly. They need to take data a couple of times. But by the end of this one, especially with the reinforcement of the balanced forces problem to check their work (the card prompts… “Think… why?” and students took that to heart), the understanding of how to work with unbalanced forces and acceleration was practically visible in their faces.
Dropping a Sensor
For this station, students predicted the acceleration of a dropped object. We don’t do projectile motion for another couple of units, so they don’t already know the answer to this problem. The setup is very simple for this one—just an acceleration sensor (I think the one pictured here should work, though we used a WDSS when I did this in class) and an instruction to CATCH the sensor before it hits the ground. (Teamwork!)
Cart on a Ramp
Students measure the angle of the ramp and predict the acceleration. They check their prediction with a motion detector.
Although you (obviously to physics teachers) don’t need the mass to do this problem, for students who don’t yet know trigonometry and need to solve by drawing the vector addition diagram to scale with a protractor benefit a lot from knowing the mass. (It’s still possible, of course, without the mass, but it adds a level of abstraction to their work that most aren’t ready for in November.)
Two Exit Ticket Stations
The exit ticket station was useful last time, so I included two exit tickets this time around. In both problems, Fnet is not equal to any one force. The images of the pages and the editable files are included later in this post with the station cards.
Most groups were able to spend time at every (or almost every) station. Everyone did at least one of the exit tickets, and most students did both. This all happened in one 65 minute class period.
I made sure that I had more stations than groups so that I didn’t have to make each group spend the same amount of time at each station. The groups chose when to move and which station to attempt. That arrangement worked for the size and nature of my classes, but could easily be adjusted in a different situation.
After my Balanced Force version of this activity, it was clear from the exit tickets that students “got it” from the work that day. After this activity, with the more complex problems and the forces at angles, I wanted to make sure everyone got a second chance to see and discuss the problems and solutions, so we whiteboarded the stations during the next class.
Here are some whiteboards with their (awesome) work, excellent annotations and notes, and very important doodles.
In refreshing the design of my 10th grade Physics course, one thing I have been attempting to do is find new ways to replace worksheets or problem sets with different sorts of activities, especially ones that promote more group work and discourse within groups. (See kinematics card sort, momentum card sort.)
For my Balanced Forces unit, I replaced the Newton’s 1st Law problem solving with a set of lab stations. These were mini practicums where students could solve a problem and immediately check their answer against the reality of the situation.
Description of Each Station
Hidden Spring Scale
A known mass hangs from a hidden spring scale. The card is taped at the top so that it can be easily lifted to check the answer.
To increase the total number of stations, I set up two or three of these with different hanging masses.
Note: If you have the sort of spring scales that are in my photos—you can do what I did when I used them in class—just put masking tape over the back of them so it isn’t easy to see through the back and make the reading.
Hidden Hanging Mass
An unknown mass is hidden in a box and hanging from a visible spring scale.
I made the box from index cards and tape. The front panel can be easily lifted to check the answer. Another option is a toilet paper tube—the perfect size for covering hanging mass sets, but not as easy for students to reset after they use the station.
Horizontal and Vertical Forces
A known mass hangs from a hidden spring scale. It is pulled left and right by spring scales—one hidden and one visible.
Hanging Mass on a Hoop Spring
A known mass is hanging from a visible spring scale and resting on a hoop spring that is attached to a force sensor.
When I did this one in class, I used my computer for the force sensor and just taped an index card over the output on the screen.
This station turned out to be the “aha!” moment for most students during the activity.
Hanging Mass on an Electronic Balance
A known mass is hanging from a spring scale and resting on an electronic balance.
I didn’t try this station in class. It’s a new idea this summer for the next version in the fall. It should bring up good conversations about what the balance really measures. (This box is the same one from the earlier station.)
Tension Force for Atwood Cart
A cart on a track is pulled by hanging masses suspended over pulleys on either side of the track. A hidden spring scale is between the cart and one of the hanging masses. (Alternatively, the spring scale is suspended without the cart.)
In class, I tried to do this with only one pulley and with a friction pad added to the cart, but it wasn’t very successful. The version here is what I plan to try in the fall.
One station, which couldn’t be chosen until trying at least 3 of the other stations, was an “exit ticket” station. It was done individually and not graded.
Since I was replacing a problem set with these stations and wouldn’t get as good of a view of what students were thinking, this gave me some insight into whether or not this experiment was successful. (The evidence I gathered pointed to it being pretty successful.)
Station Cards and Exit Ticket Files
For a project that I am working on with Mark Schober this summer (much more on that in a few months), I created new documents for station cards and exit ticket files. Here are images of those pages:
The cost is $25 for the day and includes food. You don’t need to be a current member of AAPT or attend any other part of the summer meeting (though we encourage you to look into both—especially the HS Physics Teacher Day on Monday if you’ve never been to an AAPT meeting before). Everyone who attends the camp gets to share and learn from each other, and we even include work time at the end so that you can start turning your new ideas into action before the day is over.
In my (admittedly biased) opinion, there is no better 1 day professional development for HS physics teachers. I have learned something every year, and my students have definitely benefited from this event because of my improved teaching and classes.
Here are my blog posts about the camp from 2017, 2016, and 2015.
One of the best things about my current school is that the students push me to rethink practices that I’ve taken for granted in the past. They even push me to rethink practices that I’ve put lots of effort and intention into developing, like my final exams.
“Can we have a group test?”
I’m in my 3rd year at this school, but as we neared the end of my first trimester here, my 10th grade physics students wanted to know what my final would be. They told me that at a progressive* school, I should give them a project or have them do a presentation. Neither of those sounded good to me, but I heard them asking me to come up with something that wasn’t just a test. What I did for them that year was one of the seeds for what I’ve been creating these past two years.
The last piece came from trying to think about what I valued in my class and how that lined up (or didn’t) with what and how I assessed my students. What would a performance task look like for this sort of class? What does it mean to have and show mastery in a high school physics class?
Final Assessment #Goals
After thinking about it, here’s what I decided that I wanted to accomplish.
The exam should be an experience, not (just) a test. It should be a performance-style assessment.
Students should get a chance to see that the problems they have done on paper really do work in the “real world”. They should see that physics lets you make predictions that check out.
Our class is a collaborative experience—so our exam should be, too.
Students should get to experience and feel some success in applying the skills they’ve learned.
The final assessment is a performance—it should be (at least a little bit) fun!
I already have a good idea about what each student can and can’t (yet) do individually because we assess a lot. (19 quizzes in 10 weeks. Seriously. A lot.) Another data point of the same type probably wouldn’t help me or them learn anything new, so I figure that I should try measuring differently.
So. Here’s where I am now. I started trying this new format last year in my one-trimester long 10th grade physics classes, but I’ve refined it this year in my yearlong mechanics and chemistry classes. I’m going to talk about it from the physics point of view here to start (and I plan to give more details in future posts).
A Collaborative Lab Practicum Group Exam (11th Grade Physics: Advanced Mechanics Version)
When the students enter the room for the exam, they choose a card with a number on it. Then they go and sit wherever they find the envelope that has the number they chose. The tables are grouped together to make the best use of space in the room, so students are sitting near each other, but no one at their table is going to be in their group during the rest of the assessment. The groups are totally random, and I have no idea which students will get which tasks until they are starting the test.
Part 1: Individual Planning or Warm-up Exercises
The first part of the exam is done individually. Students open their envelope and work on whatever they find inside. I usually give them around 15 minutes or so, and I let them come in a little early if they think they might want or need extra time.
In the fall, I had students spend the individual portion planning for their task. They couldn’t take any data or make any measurements. They weren’t supposed to “solve” the problem yet. Instead, I asked them to decide which models seemed most useful and draw the diagrams corresponding to those models for the situation at hand. They could start making a plan for how their group might approach the task.
I liked the idea of individual thinking and planning before getting started in groups, but I didn’t think it was working very well the way that I was doing it. Some of the tasks are difficult to understand when they are just described on paper (or it really makes more sense to interact with them first and maybe make an initial measurement or two before really getting started). Almost none of the groups seemed to follow plans that had anything to do with what the individual members wrote ahead of time, and I wasn’t sure whether the solo planning was helping them be more successful as a group.
Except for how closely the students are sitting to each other, this photo actually looks like an “exam” that I might have given in the past.
For the winter, I took a different approach to this first part of the exam. Instead of a description of their task, each envelope had a page of warm up exercises that were loosely related to aspects of the task that their group would be assigned. It would have been difficult for a student to predict their task based on just these questions, but I was hoping that it would get their brains going and ready for more challenging physics.
In any case, students turn in their paper and envelope before moving on to the next part. Since the next part involves groups, they have to wait for a few minutes for everyone to be ready.
Part 2: Group Lab Practicums
Once I have everyone’s envelopes, I give them a brief orientation about which task is in which part of the room so they know where to go. (They either knew the task in Tri 1 or the group number that they were assigned in Tri 2 from what was on the paper in their envelope.) I spread these stations around the room and try to use the space as best as I can. I’ve put some tasks in the hallway before, too. This part is where they first find out who is in their group for the test.
This is the synched harmonic motion group in Tri 2.
In Tri 1, I had 20 students in the class and split them into 5 groups of four. In Tri 2, I had 21 students in the class (long story), so I split them into 7 groups of three. The smaller groups were much better, so I’m going to aim for groups of three from now on. In both cases, every group had a totally different task.
A group trying to figure out the hidden hanging masses in Tri 1.
Each task comes with a single instruction sheet and some loose leaf paper.
Here’s an example of a Tri 2 task info sheet.
Since all of the groups have different tasks, I need to be sure the info sheet has enough on it to get them started without me being there to explain much. For the first part, I mostly spend my time going around and observing to make sure each group is understanding what the task is asking them to do. After a while, I’m doing that, talking to groups a little here and there, and being present for groups to test their results.
This Tri 1 group had a lot of arguments and were eventually successful in their task.
Many of the groups had multiple tasks to complete. I wanted them to have too much to do so that most groups wouldn’t finish everything in the time that we had. I wanted them to work the whole time and feel that they were doing something that was still in progress, especially since this class wasn’t ending after the final. Even though it was a ton of extra work for me, I wanted every group to have a different task so that groups couldn’t compare themselves to each other for being faster/slower/”better”/etc.
I’m going to save the descriptions of which tasks I chose and what I was looking for to make a good exam practicum for another post (since this one is definitely getting long enough already).
Here’s a Tri 2 group figuring out how to hit various carts with pendulums.
One improvement that I made in Tri 2 was to tell them that they shouldn’t be turning in their scratch work. They could do scratch work wherever they wanted (and I put paper and whiteboards at every station to help facilitate that), but once they thought they had a solution, they needed to sit down and write one nice copy for me that I could actually follow. In the first trimester, following their work was nearly impossible since so many students were working on so many papers and there was basically no way to know what order any of it happened.
Part 3: Individual Reflection
Near the end of the (two hour) exam period, I stopped groups if they weren’t already finished and asked them to help me clean up the room and to do an individual reflection about the activity.
For the winter exam, I did a Google Form instead of a paper reflection. I asked:
How did your group do at your task?
How did your group do as a group?
How did YOU do today?
I also asked them whether this exam gave them an opportunity to use different ways of being “smart” in physics, whether they would prefer a more traditional paper-and-pencil test, and gave them a chance to tell me about anything I hadn’t asked specifically.
The options were: Posing interesting questions || Making astute connections (between seemingly different ideas) || Representing ideas clearly (so that others can follow and understand them better) || Developing logical explanations (building arguments and using evidence) || Working systematically (taking an intentional approach to think about all parts of a problem or situation) || Using multiple representations and translating between different representations || None of these
Here’s a sample of some of the things they wrote in response to the first set of questions: