In my last post I talked about how I finally reenvisioned collisions and explosion problem solving for my on-track physics. It went so well I’m definitely going to integrate more of it into AP.
The goal of the reenvisioning was to set students up for a meaningful tennis ball cannon launch lab at the end of the lesson sequence.
If you’re unfamiliar, you create a tennis ball cannon, launch it, and have students calculate some quantity based on momentum conservation. To be honest, I haven’t run this lab since my first few years teaching for a few reasons. One was that my cannon got stolen at my first job. Then I decided that whole class labs are less effective than small group work and I hate when it looks like everyone is copying answers. The activity just wasn’t meaningful enough.
But after talking to several friends, everyone was excited about the idea of a cannon launch, so I spent my weekend rebuilding a cannon.
To open the lesson I set up and demonstrated an “explosion” with our car-track system. I ensured that one car had more mass than the other and we had some conversations about what to expect. We also talked about what the equation would look like based on our previous experiences with elastic and inelastic collisions. Students were able to correctly determine that it’s basically the opposite of an inelastic collision.
Next, I gave them the scenario where the cannon had a mass of 4.0 kg, the ball had a mass of 1.0 kg and the cannon’s launch velocity was 5 m/s. These numbers were strategically chosen. I wanted to keep whole numbers and also have a cannon-ball ratio that was similar to the actual cannon-tennis ball.
Students then completed the four representations as we’d previously done earlier in the week. Below is a student work sample.
The great thing about this was that students were able to accurately represent and predict the outcomes of the cannon-ball system before we got into the muck. This got students thinking individually and talking in small groups. We also discussed why the results made sense.
To launch the cannon I let it go through a photogate to snag the post explosion velocity and then students completed the calculations.
For the post-lab analysis I threw in a few thinkers. They included:
Find the average force on the ball
How would a longer cannon change the ball’s launch speed? Explain in terms of impulse-momentum
If we used the same cannon but filled the tennis ball with rice, what would happen to the speeds of the ball and cannon post explosion?
You can see a sample student response below:
These questions led to some really great conversations that brought us back to equal forces, equal momentum changes and where time falls into the mix.
The first set of posts I wrote for this series was about momentum because I made such a large shift from how I used to teach to how I currently teach.
In the same vein my teaching of forces has also changed.
In the past my force unit looked like this:
Inertia Day! Lots of Demos, initiation into the inertia club with club cards (you hold the card on your index finger with a penny on top and figure out how to flick the card out from the penny)
F=ma. Define it, notes, define force diagrams, practice force diagrams. Practice F=ma problems.
One day on action-reaction. Gloss over it; “it’s easy”
I cringe writing this out now. It was so boring! Inertia and action-reaction felt like fluff. We don’t need fluff!
Currently, my unit structure is designed with the big ideas in mind. (Because, tenet 3: Order Matters, Language Matters) I was excited to see that the idea that teaching in a structure that models the thinking we are targetting to improve outcomes is actually supported by research, so my model draws on Lei Bao’s frameworks for force:
One of my biggest frustrations was students putting random “F(applied)” on force diagrams. It irked me to no end!
So starting with the framework for Newton’s Third Law, I turned my force unit on its head. The fundamental piece we begin with is:
A force is an interaction between objects
Observational Experiments
We start with the activity from Pivot Interactives where two cars collide.
Students are asked to separately write what they observe about the car motion and also what they observe about the force acting on each car.
After making the observations we discuss.
The primary aspect students recognize is that heavier/faster cars result in bigger forces. That’s all well annd good, but what about the force that each car experiences. Even though they’ve literally just witnessed and recorded it, they still want the heavier one to hit harder than the light one within the same collision! We closely observe this together and see that, indeed, the forces are always the same.
This is what allows us to define a force as an interaction between objects. Without a second object pushing on the ring, the ring won’t squish. Since the force is something that happens between, it must be equal and opposite.
This very small shift has been a game-changer. It is very rare for me to have students putting totally random forces on objects because “it should have one”.
From here we dive into Eugina Etkina’s ISLE cycle.
Students are asked to hold a heavy and a light object in each hand, palms up and then represent those objects with arrows on a diagram. Students are asked to label each arrow with the object interaction. This is a fun one because a lot of kids are quick to label “gravity” but when I inform them that gravity, is not in fact, an object, they have a moment of pause. Eventually all students arrive at the correct diagrams: equal sized forces on each object, bigger forces on the heavier object.
From here I diverge between AP and regular physics. In regular physics we will go directly to the mass vs weight lab where students will ultimately derive the expression F(earth) = mg. With AP we continue to follow a modeling cycle with experiments with a bowling ball down the hallway: rolling, constant force forward, constant force backward. Then I ask how we could have constant velocity AND constant force. Students are quick to say “push down” (and we are fresh off of projectiles where x and y are independent!). Then realize if we alternate “taps” that will do it (balanced forces). Students are asked to represent and reason by drawing a complete motion map, an accompanying force diagram and then look for patterns. In this way students then recognize that balanced forces will result in constant motion (including v=0) and unbalanced forces result in accelerations. For homework students will complete two exercises from the Active Learning Guide from Etkina’s book where they will continue to practice drawing motion maps and force diagrams together in order to find relevant patterns. From here we get ready for labs!
Up next… labs labs and more labs! Quantitative Experiments with Forces
A few weeks ago I posted the article We Did Improv in Physics which outlined my four-day mini-unit emphasizing communication and presentation skills. Students did this in a number of ways including deconstructing TED talks, writing a blog post about their research, and giving a two minute impromptu version of their talk, in addition to the improv workshop. While the energy and the feelings in the room were fantastic, I also collected survey data from students that I’m going to share here.
Overall Results
Before we started the unit I asked students a number of questions around presentations. One of the prompts ask students to rate their confidence when presenting in front of peers from “Very Anxious” to “Very confident”. When the unit ended I asked them how they were feeling about presenting their physics projects. The results were astounding.
While the four day experience wasn’t quite enough to build substansial confidence (increase from 39 to 52%) the amount of anxiety significantly decreased from 42% of students reporting some level of anxiety to only 14%. About half of these students moved from anxious to neutral and the other half moved from anxious to confident.
Students were also asked to rate the statement “Being able to give presentations is an important skill for me to acquire” the number of students who marked “very important” doubled from pre to post assessment.
Students were also asked what the single, most important aspect of an excellent presentation was. While many of them stated “audience” there were also a great deal of other responses such as confidence but also things like structure, organization, and knowing your own material well
After the mini unit these responses were reduced to those that were emphasize from the lesson. An increase in the response “audience” was noted as well as an increase in mentions around the visuals. Noticeably less was “confidence”
Student Feedback On Activities
Students were prompted “Considering your final presentation, how valuable were the activities around dissecting the various talks?” Student rated on a 5 point scale from “not valuable at all” to “very valuable”. A summary of student responses for each of the three activities is below.
Turn Your Paper into a Blog Post
56% of students found the blogging activity to be useful, with only 8.7% of students reporting it was not. Some of the comments are below with scores in parenthesis:
It helped to see how there was a different type of communication between presentations and the lab report itself. (4)
It helped show us how to communicate our project in an understandable, engaging, and quick way. It used common language like our presentation will. (4)
I felt like the activity where you turned the report into the blog was helpful because it showed how you would convey your report to an audience rather than someone reading it just for information. (5)
By doing the blog post and using informal words I realized that this physics presentation was more like a conversation between our peers. We were just sharing our finding with one another and the blog post helped organize all this information. (4)
Interestingly, the students who rated the activity low still reported the value in the activity’s intention, demonstrating that the low score had more to do with their perceived needs than the intented learning.
It was somewhat helpful for making the presentation interesting and easy to understand. However, I didn’t find it helpful for actual content which I’m more concerned with. (2)
Data Viz Presentation & Evaluation
87% of students found the Data Viz presentation helpful. I think this is interesting because this was the one “lecture” that was provided and I know my students tend to prefer lectures. Still, there were some great reflections from students:
I did not realize how much detail is given into making slideshows. For example, I would have never thought about making slides colorblind proof. (4)
I especially liked this activity because it enabled us to visualize what we could change in our presentations through using new strategies. I especially found important how we learned to use less words and things on each slide, making them simpler. Also, the rule of thirds was a good guideline for how we laid out our slides. (5)
It helped to see the ways the data can be shown to not over power the audience with so much information at once. (5)
Improv Workshop
48% of students found the improv workshop to be helpful with only 8.7% reporting it was not helpful. There are a couple of pieces of evidence from the commentary that support these low numbers, even though there were drastic results observed in the pre- and post- presentations. Firstly, the intention of the activities was not clear to students until we debriefed. We did improv on a Friday and debriefed on Monday. Secondly, the workshop put students very far outside of their comfort zone.
Overall Impact
Overall students were very positive towards the mini unit. A few comments of note:
I think it was really valuable to have this unit because none of our other teachers really sit and go through what a generally good/well-rounded presentation should look like, they only focus on content/course specific presentations
It felt like a breath of fresh air, and made me realize that communication is a huge skill in in physics apart from problem-solving obviously.
I think that unit is helpful when it comes to sharing your findings with other people in an effective manner. I learned quite a bit about how to construct my slides to show only the important information. This unit is also helpful in feeling more comfortable presenting in front of your peers.
Students were also asked if I should run this lesson again. Every student except two said “yes”. The two exceptions marked “maybe”. Of note is that the two “maybes” expressed discomfort with the improv workshop, but had generally favorable commentary regarding the other activities.
Honestly, the results are beyond what I was hoping for. This is something I will absolutely continue.
I have this lab I received from a colleague, it’s an iteration of a lab I’ve seen in other places. Basically an object goes down a ramp, gets caught by a paper catch/index card etc and students are looking for some iteration of work and energy.
In the version I have students are asked to find a relationship between height and distance. The cool thing about this is it ends up that height is directly proportional to distance and related by the coefficient of kinetic friction alone.
Student’s work looks like this:
Students are asked to complete the lab with a hot wheel car and then again with a small mass attached to the car. To students’ surprise the lines are not identical. This really bothers students until we discuss what we were actually looking for. See, the lines are still parallel, but the car with more mass is going to have a greater momentum at the bottom and will require a greater impulse to stop. It’s a fantastic conversation piece.
Student generated graph from lab
I really enjoy this lab because it requires students to consider a new problem and then apply that knowledge to a lab setting. Research has shown that students don’t really learn content in the lab, they learn lab skills. I was always a little frustrated with the disconnect between all of the work students put into the theory and then the lab results themselves. So this time I changed things up.
Instead of giving students the lab hand out and letting them work in groups, when students walked into the room they were put into visibly random groups. Visibly random grouping just means you create the random groups in front of students so they see it was truly random. I’ve been immersed in the book Building Thinking Classrooms and the research on this is really cool.
Once students are in their groups and at a white board that is vertically mounted, I’m in the middle of the room at a lab table with the lab set-up. I verbally explain the set up and that I want them to derive a mathematical model for the relationship between height and distance.
Vertical whiteboarding is really cool and has several advantages. First, students are standing which puts them into a more active position, this gets more of them working. Second, it’s really easy to just look around and snag ideas from other classmates. Third, since they’re already standing it’s really easy to move around the room and discuss with other groups. The first time I did this what astounded me was the sheer number of students talking. Instead of it being maybe 4 or 5 leaders it was nearly everyone in the room! There was so much collaboration and ownership of learning it was magical.
Taking a peek to get ideas is easy!
So I did this with the first part of the lab. Next, I asked them to sketch what the graph will look like with the two lines. Almost all of the students sketched the two lines on top of each other. I want them to have the experience of their data not aligning with their previous ideas and having to reconsider, so we left it at that. Then students were off.
I’m going to finish this lab this week, so I’ll have to come back to update this post, but I love this activity and vertical whiteboarding gets a 10/10 every time.
It is the end of July, the back to school sales have been running for a month, the #clearthelist movement is in full force. While I keep telling myself I have ALL of August left (that’s actually a lie, I have institute the 30th/31st) many of us are starting in just a few weeks. Here are three ideas to start physics strong. These ideas are grounded in my values and beliefs around teaching physics. You can read about those here
Physics is about EXPERIMENTS
I want students to know science is investigative and that anyone can do it. Many teachers will do a team-building activity on the first day, but I prefer to let students play. This gives me a chance to observe the dynamics of each class before I begin to influence the room and it also takes any pressure off of students to perform for one another or myself. I try to set up a demonstration or lab from each of the units for the entire year. Directions for observations are left on a notecard in front of the set up. Students are asked to write down detailed observations about each demonstration. Over the weekend I ask students to find the demonstration online and learn about how it works. Students are then asked to write a claim, evidence reasoning statement about a single demonstration. Here is my handout and some of the demos I set up
Getting to Know You
When we begin class I ask students to introduce themselves, rather than butchering their names on the roster. I take notes for myself. I ask students to share their name, and how they are feeling. I will also ask them to create a flipgrid introduction with a little more info. This allows me to have their pronunciation recorded so I can review it repeatedly. Here are the prompts:
1) State your first and last name 2) What is something you’re really into, or “your thing?” This could be an interest, hobby, job, talent, etc… anything! 3) Post a picture in your video of you doing your thing or a product from your thing 4) What is one thing you wonder about one (or more) of the demos from the first day? (I wonder why….) 5) Respond to at least TWO classmates!
Physics is for Everyone!
I am a STEP-UP advocate and one of the lesson plans in the program is the Careers in Physics. In the lesson students learn about the vast scope of employment opportunities with a physics degree and then are asked to create a career profile. Students do this by taking a super short survey where they check off their interests and values and then they are matched with a professional who shares their interests. You can access the lesson plan and resources here.
I hope you find these ideas useful! What else have you done to set the tone for the year? Drop it in the comments!
In this post I will outline 3 activities I do in my classes. Each serves a different purpose and function depending on the group of students, but most could be used interchangeably between levels depending on your own goals. They are the following:
Pivot Interactives: Ball on a Wall
Popper Lab
Egg Drop Challenge (with a data-driven testing phase)
These activities are all about giving students a “real-world” opportunity to collect data and calculate quantities from the course. There’s not a lot of “discovery” going on here, a primary driver is practice. However, each activity presents rich opportunities for different conversations.
Please don’t steal for profit on TPT. That harms the teachers who share, those who are in need, and our profession as a whole.
Pivot Interactives Activity: Ball Against a Wall (regular level)
Many of us came on to Pivot Interactives after the original library was migrated from “Direct Measurement Videos” many more of us came on to PI when we had to teach in the pandemic. If you can push for a subscription it’s very much worth it. Labs that are too expensive or cumbersome for a class set become attainable, make-up work, homebound, remote learning… you name it. There are a lot of benefits. I love this very simple activity that just involves a ball colliding with a vertical wall. Important note: I don’t use the built-in questions/grading set up in pivot. It’s very well done, but I find that computer work usually hinders collaboration, so I moved away from having students answer in pivot even before the pandemic.
Ball against a wall in Pivot Interactives
Students begin this activity by reviewing the transformation of F=ma to the impulse-change in momentum relationship. The mass of the ball is provided and students have access to a ruler tool and stopwatch. There are a lot of ways this could be done. For my regular students I have them determine the pre and post collision velocity as a simple x/t calculation (we verify it’s moving constantly by seeing it move equal intervals down the ruler in equal frames). The biggest challenge is determining the time of the collision. This is one thing I love about this activity. In day to day life collisions happen so fast we don’t really consider the impact lasted for a measurable time. I love how this visualizes. You can see my original handout here. Last year I discovered that remote students do better when labs were broken into very small tasks through jamboards, so also check out thejamboard activity here. (2026 Update: Take a look at some of my new summaries for pivot activities!) You will notice a lot of scaffolding. This is necessary for my regular level students, but it may not be for yours. When I run this activity in AP I simply inform them of the goal and send them on their way.
Popper Lab (APP1)
I took this lab from an AP summer institute I attended under the direction of Martha Lietz. Students pop a popper toy (the half-spheres you turn inside out). The ultimate goal is to calculate the time for the “pop”. While students end up using impulse-change in momentum, they also have to use kinematics and F=ma along the way. I find that many students have a hard time with this interleaving because up until this point (remember I do momentum right after forces) we haven’t had too much of a chance to interleave yet. That is one of the main reasons this lab has been a mainstay for me, even if it’s really just a “glorified homework problem” as I tell my students. Students are taken step by step through the process. See the activity here. At the end of the lab I ask students to submit their calculated times to a google form where I aggregate all of the responses. We will first do a quick skim on day 2 so if students calculated an egregious answer, they can obviously see they need to check something. Once we remove the outliers, we do an average and standard deviation. It’s SO COOL to see how close student answers all are when it feels like such an imprecise activity! Because this is a glorified homework problem we can take some time to have a solid conversation about measurement, uncertainty and standard deviations, making it appropriate for AP.
Egg Drop Lab
Whenever students hear we are going to do the egg drop they respond gleefully “we did this in middle school!” I am quick to explain why this is not like middle school and the middle school experience was not like science. In middle school students are typically given tons of supplies, they can use as much as they want and they just cobble whatever together and start chucking. Can you imagine if engineers did this? What a waste of dollars and materials! Besides, you shouldn’t even think about messing with materials unless you have some kind of idea about what is going to happen.
I explain the parameters: 5 sheets of 8.5×11 paper and 1 meter of masking tape. The device must be attached to the egg. No parachutes.
The reason for these parameters is I want students to be thoughtful about the why behind their device.
But no devices are built without prototypes!
So on day one we have a testing phase. (See handout here) Students use force probes and cars or iOLabs and run “prototypes” into the probe (see image below for how I set up the probe). This might be folder paper, crumpled paper, tubes… whatever! But we know that our eggs will be saved by one thing: increasing the time of impact and decreasing the force.
This activity is by no means precise, but it gets students thinking about what to actually do with the paper.
On drop day students have roughly 35 minutes to build their devices which we drop in the last 15. Students present their devices to their classmates and then drop from 2.0 m. Eye of the Tiger plays on loop in the background.
Egg drops in physics today! Students tested how to use paper to increase collision time in order to decrease force to protect an egg! Today they got to drop! Next year I’m totally using wrapping paper! 😆 #iteachphysicspic.twitter.com/JWbu93bDv9
The following day I ask students to whiteboard diagrams of their devices that also show where the egg was located. We discuss the designs in relation to their smashing or success. View the activity here.
None of these activities are ones I would consider particularly awesome and certainly not flashy, however often its these kinds of activities that allow the nuances to shine.
At an AP Institute I was introduced to the demonstration where you roll different cans down a ramp and a can of broth is ridiculously fast compared to others. The reason, of course, is that the low viscosity of the broth means the liquid does not spin. In turn the fast majority of the can + contents has translational energy only.
I wanted to do something more with this excersice than “guess which is which”. After some poking around I settled in on this lab that I now run each year. Be forewarned: the results aren’t spectacular, but the lab comes back with great data and a great experience. Students regularly report this is their favorite activity of the year.
We start by laying the foundation of the race. I have 5 cans: An empty can with the lids off, an empty can with lids, refried beans, condensed cream of mushroom soup and chicken broth. I provide students with the following information and ask students to rank by which gets down the fastest.
We share results and comment on similarities. Groups generally predict the empty can without lids will be last, but the rest gets messy. Did students put the refried beans because it was a cylinder or because it has the greatest mass? Where do you put the broth (many throw it in the middle). The cream of mushroom soup has a smaller diameter.. how does that matter? We’ve talked about all of this already, this is a great application.
After our discussion (mass is irrelevant, radius is irrelevant) we talk about modeling each can. The empty cans and the refried beans are obvious: hoops and cylinders. But what about the mushroom soup? When you dump it out you get a cylinder of soup in the pot, so it’s like a hoop + 2 disks + a cylinder of soup. We race the “obvious” ones…empty vs beans, empty + lids vs mushroom soup. Then we race the winners and losers… empty first. I poll the class about the beans and soup. It’s a 50-50 split. I tell them this is a good guess. We have tot race best 2 out of 3. Beans wins by a hair.
Then enter the broth.
After broth is the hands down winner, we talk about what’s happening. What is the liquid DOING? (Many studnets think itt’s spinning like a hoop). I demonstrate with a VOSS bottle and dyed water (VOSS is nice and smooth).
For homework I ask students to develop an expression for ANY object down the ramp. How can we do this? Well one thing worth noting is that every moment of inertia is some object MR². So let’s replace “some number” with k. I tell students they need to figure out the expression and what they will plot to yield a straight line and what the slope will represent.
The next day we review student work. It’s a cool derivation.
We get down to the fact that students need a graph of v² and height. Ok cool. But how will we compare our results? We go back to the models. Students are responsible for coming up with the velocity at the bottom of the ramp for their assigned can. For this activity I put students in ability-level groups, assigning the empty cans and the beans to the students who are usually C and lower, the broth to my B students and the mushroom soup to my A students. (more on that choice another day). After students have a chance to work through their derivation we review all of them. One of the things we discuss previously is that when determining velocity at the bottom it’s always the √number*g*h and that number is between 1 (hoop) and 2 (sliding only). The numbers we get all fall in line with our expectations and observations…including why mushroom soup and refried beans are such a close call!
Student work for can of chicken broth.
Before we begin the lab we need to have a discussion about reducing error. We have a major problem. Height is easy enough to measure with little uncertainty, but we are looking at an expression with final velocity SQUARED. This is problematic for several reasons. First, the square means that uncertainty is going to propagate and blow up. Second, we’re looking for FINAL velocity. Cherry-picking that data point is sure to be messy with tons of uncertainty and, frankly, a waste of our tools. So what IS consistent and reliable no matter what we do? Students quickly realize it’s acceleration! We know how to best collect that data from other labs: run a regression through the position or velocity graph. We can then use a spreadsheet to manually calculate the expected final velocity for a specified distance.
Students are able to get data that generates amazing straight lines and then they use that data to determine the moment of inertial of their cans.
Student data for chicken broth
Some of the cans will be pretty far off from the theoretical models, but that’s ok! We tried to really simplify something real and complex! (The original idea from which I got this the activity used cans filled with concrete and other materials that are much closer to the models.)
Physics.Teacher.Momma. 