One of the more challenging standards for the nuclear physics topic in my IB Physics class is calculating the binding energy per nucleon based on the mass defect of a nuclide. I've done by best to help walk students through the concepts in the second lesson of my Atomic Physics Unit but this is one concept that you really need an opportunity to try it for yourself :) To help my class with this focused practice, I put together 30 self-checking examples for them to crowdsource and create a "Binding Energy per Nucleon vs Mass Number" scatterplot that we can reference later during our discussion of fusion vs fission. The DataThe first task in assembling this activity was putting together a valid database for nucleus masses of different element isotopes. I wanted a good range of masses to be able to see the characteristic shape of the "Binding Energy per Nucleon" graph so I came up with this list of 30 examples. I put this together several years ago, and I honestly don't remember where I assembled this data from originally
I give all students access to this database of masses and assign individuals or groups to different portions of this list so that there is no overlap within the class. I have also done this in pairs where each group of two starts with one and then I keep giving them new assignments as they complete their element. Automatic FeedbackThe feature that makes this activity powerful is once students have calculated the binding energy per nucleon for their assigned element, they enter their value in a google sheet that provides instant feedback. If their answer is within 5% of the actual value (stored on a hidden sheet) the cell to the right of their answer will turn green and display "Y" for "yes". If their answer is outside of the range, they will see a red "N" for "no". Since there are so many different ways that this calculation can go off the rails, this built in feedback prompts students to revisit their work and/or get extra support from a classmate or teacher. When I run this activity, I make a copy of the google sheet for each of my classes and I provide my students with a link to the document so they are all updating the same communal "answer sheet". If you don't have access to 1:1 technology, I have also done this activity by having students enter their answer in at my computer in the front of the room. Click below to make a copy of this google sheet with the instant feedback pre-programmed in ⬇ In addition to providing feedback on their answers, the google sheet also creates a graph of the Binding Energy per Nucleon vs the Mass Number in real time as the data is entered in. When it's all said and done, the data from this activity can be assembled to make the graph below. I save this and return to it once we start talking about fission/fusion. :) Files
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You may be wondering, why not just give a traditional individual exam more similar to the actual IB exam? Good question...
Ok, once I decided to give it a shot, I needed a way to make this task truly groupworthy so that all of my students could valuable contributors in groups of 4 or 5. To make this happen, I developed a workflow to facilitate the groupworthiness of the activity. I will attempt to outline the "phases" and my thinking behind them in the post below :) Set UpThe Questions This starts with a traditional test that is a little longer than something you would give to students with the given time provided. When I did this, I had a two hour finals block and I assembled a 48-question monster of an exam. I then cut the test apart into 48 individual questions made bundles that contained every 5th question from the exam. Each student in the 5-person group would start with one of these bundles to ensure they would see questions from each topic at least once. Unfortunately, this part is a little tedious and it takes a little prep work but I can justify it by watching a movie and remind myself that it is still less time than the extra grading that it would be for individual exams. ;) The Groups To make equitable groups, I exported my gradebook and sorted by overall semester grade. Once in order, I distributed the students in to groups by numbering them off and assigning them to groups so all groups were mixed.
Phase 0Once all names were recorded, they had a couple of minutes to read through the instructions. Phase 1This process starts out pretty individually with students working through their prepared bundles of every 5th question on the test. Since I didn't have class sizes perfectly divisible by 5, groups of 4 had a bonus packet to divide up among the students that made it through their bundles first. Tip: some groups figured out that it would help them later on in phase 2 if they wrote their initials in the top corner of the problems that they worked on so that they knew who to talk to when evaluating each other's work. Phase 2Once an individual student was done with their initial bundle of problems, it was time for them to move on to phase 2. In this phase of the task, students review each other's work by pulling questions from the piles. As more group members contributed, these questions naturally moved up the confidence scale. Eventually, once groups felt confident in a problem and it had been seen by at least two group members, they could place it into a bin just to get it off of the table. Phase 3
GradingI graded these tests in the same way that I would a traditional test but I entered the score with a much lower weight than the other tests that we had throughout since I still wanted their overall grade to be an accurate measure of their individual understanding. Most of my exams are around 35-40 points and I entered this one out of 10 points so it didn't have as much impact on their overall grade but was enough that they still cared. As I explained it to them, "It's enough to matter, but not enough to MATTER." ;) All students in the group received the same grade for this assessment. Support and ResourcesAs I mentioned above, I've used this strategy in place of a traditional final exam. Since we didn't have time to review for this cumulative assessment, I decided to build in layers of resources that groups could use throughout the task. 1st Half For the first half of the challenge, students were allowed to use their calculators, equation booklets, and study guide binders that we have been building throughout the year (see Content Guides for more info on these). These resources had important reminders but no example problems or detailed walk throughs of the content and provided just the right level of reminder for them to confidently move forward on most problems. 2nd Half In the second half of the time, I allowed all groups access to their notes and course materials posted online. By postponing the time like this, they were able to go back and check or relearn the material for the problems that they were still unconfident about without turning the whole activity into a mindless scavenger hunt from the beginning. ReflectionThe thing that I'm happiest about with this group assessment approach is that the level of engagement was super high throughout the entire 2 hour finals period. Students even noted how fast the time went by since they always had something new to do as they progressed through the different phases. It turned a situation that is In the end, I was so happy with how it all went. Students took a deep dive into a semester's worth of content without the stress of a traditional final. They also got valuable experience reading, evaluating, and correcting each other's work in the process! Files
This post is part of a series that I'm hoping to continue where I outline some different teaching strategies that I love separate from specific lessons Click for More Teaching Strategies
Newton's 1st LawAn object in motion stays in motion and an object at rest stays at rest unless acted on by an unbalanced force Challenge #1 - "An object at rest, stays at rest"
Many of my students recognize this as the "tablecloth trick" and it's fun to see them make that connection. It isn't listed in the activity but it's also fun to try this with stacks of three of more blocks on top as well or to experiment with different launch speeds. :) Challenge #2 - “An object in motion, stays in motion”
Knowing that this one is coming, it's a good idea to set up the baseboards so that there isn't too much "launching into a crowd" going on. It's also fun to connect the rubber bands to a long board that goes down the middle of the table (like Bruce Yeany's set up) and have students aim for a target with their top block by launching it at just the right speed. Newton's 2nd LawThe force applied to an object is equal to its mass times the acceleration Challenge #3 - Race between identical blocks
It is highly recommended to have the same person release both blocks to ensure that they are released together. If the blocks still aren't hitting at the same time with this set up, it would be worth checking your rubber bands. Sometimes they wear differently over time and that can result in unintended differences in the force. Also notice that you can stow the second rubber band from block B by looping it around the pegs to get it out of the way. Challenge #4 - Double the Mass
Depending on the strength of the rubber band connection, you can sometimes see inertia at play at the top block resists a change in motion (remember back to Challenges 1 and 2) Challenge #5 - Double the Force
This one happens really fast and it's a good opportunity to try out the slow-mo method so that it's ready for the next challenge. It's quick but the double rubber band block demonstrates about twice as much acceleration. Challenge #6 - Double the Force AND the Mass
This is really the culminating event of this entire activity and SO satisfying to see them hit at the exact same time. It can be challenging to release both blocks at the same time so often if students think that one is hitting first, I challenge them to look at the slow-mo and verify that both blocks were truly released together. It could work to use a ruler or meter stick to hold them back and start them at the same time if independent hands doesn't work out. Newton’s 3rd Law Every action force has an equal and opposite reaction force Challenge #7 - Tug of War
If you have students pull the blocks back to each end of a meter stick, you can make this one a little more quantitative and actually have a reference point to show that they meet at the halfway point regardless of how the rubber bands are connected. Challenge #8 - Tug of War with Different Masses
Even though both blocks experience the same force, the double block doesn't move as far because it is more massive (think back to Challenge #4). This is what we think back to when we talk about how gravity pulls on both a sky diver and the earth equally even though we only see one of these objects moving in any meaningful amount. The MaterialsThe thing that I love best about this idea is that the materials are so simple and low-tech. There are lots of different set ups that would work just fine, so rather than put together specific step by step instructions, I'm going to lay out the general set up that I used and reasons for some of the modifications that I made to Bruce Yeany's original design. The BlocksEach set up requires two blocks that can be connected with rubber bands to the base board. There are slight differences between the two but each one has same general design. Dimensions All of the blocks are made from scrap 2x4 lumber cut into 5.5-inch lengths and sanded to round the rough edges. Lag Screw Eye I drilled a recessed 3/4" hole into the end of each block and installed a 1/2" Lag Screw Eye into the center. I chose an eye screw because I didn't want the rubberbands falling off but after I had to replace my first set of broken rubber bands, I kind of wish that I would have just gone for recessed hooks here instead... Collision Dampening In my test run before giving these to students, it was clear that I was in for a splitting headache if I didn't do something about the noise. My solution was to get a free carpet sample from Menards and tape a couple of small square to the end of the blocks. If I were to make these again, I would probably go for something like a thick felt materials to avoid the unraveling carpet. Block AThis block is used in the first two challenges requires the ability to secure a second block while allowing it to fly forward when it hits the base board. I accomplished this by cutting a short length (~2.5 inches) of scrap wood that I found that was 1/8" thick with a width of 1-1/4". I nailed this to the back of Block A so that it was loose enough to rotate into position but loose enough to still support the block. Make sure that it can fully tuck away when not in use in a position that doesn't impact the slide of the block. Block B
Extra BlocksFor each set up, I cut 3 extra 5.5-inch blocks from the 2x4 material. These blocks are used to demonstrate inertia or add mass for several of the challenges in the activity The Base BoardThe base board is constructed from scrap 2x3 material that I found for really cheap in the discard bins at Menards. I cut the material into 11-inch lengths to allow for nice packing with the 5.5-inch blocks.
Obviously an important part of this whole design is clamping it securely to the table. I was trying to do this on a budget so I cut a notch out of the top of the board so that I could use smaller C-Clamps and still secure it to the edge of the lab benches in our classrooms. This allowed me to purchase a set of 14 2-inch C-Clamps from Amazon for under $30. With two clamps per set up, this was enough for the 6 sets that I made with a couple back ups. It would have been a lot less woodworking required to just get bigger clamps through so if you have the budget for it, it's probably work the time savings ;)
Rubber BandsUnsurprisingly, rubber bands should really be thought of as a consumable for this lab. After a year worth of cycles, I typically need to plan on replacing each rubber band before I use them next time. My preferred rubber band for this set up are these file bands that I purchased from amazon. I found this 50-pack for ~$10. WhiteboardMy first year, I had students slide these blocks directly on the lab table and I ran into two small issues.
Material ListI made 6 sets of these Newton's Laws Blocks for my classroom so that I would have one for each lab bench. It's a pretty scalable project though so I will just list the materials needed for one set and you can scale as needed :)
ReflectionOverall, I love this lab (especially for younger students like 9th grade or middle school). Students genuinely enjoy launching wooden blocks at other wooden blocks and I feel good about the fact that they are getting hands-on experience with the different aspects of Newton's Laws. Having these shared experiences as we continue on with our forces unit is a wonderful way to connect all of our discussions to something "real-world". This set of activities isn't an exhaustive list of things that can be demonstrated with these blocks and I would encourage you to check out Bruce Yeany's video if you haven't yet to get some more ideas. I want to end with my favorite reveal of the lab, the fact that doubling the force along with the mass results in the same acceleration as the original 1 block / 1 rubber band set up. Soooo satisfying :) If you found this useful, you can find more lessons on the topic of "Forces" by clicking on the button below ↓
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Once it's made, you just need to connect it to a computer to send an image, gif, or looping video for students to "discover" with the right polarization orientation. Click for more Waves resources ⬇
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