Using The Conservation of Momentum to Decipher Fact from Fiction

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Students will be able to apply mathematical models to re-create eyewitness testimony of a collision between two students.

Big Idea

The conservation of momentum can be applied to a scenario in order to determine the probability of an eyewitness account being true.


5 minutes

I value collaborative team learning and inquiry. With this in mind, I ask students to move beyond learning to model collisions in terms of momentum to focus instead on the usefulness of these models. I have students address a real world scenario and to use their understanding of the conservation of momentum to determine the validity of two sets of claims. This lesson aligns with the HSA-CED.A.2 and the HS-PS2-2 standards because students have to use their understanding of the mathematical models for the conservation of momentum to conclude which scenario is more likely in the exhibition of "The Art of the Boom-Rush". This lesson connects to others in this unit on momentum and its conservation because students leverage their understanding of the connection between momentum and elastic and inelastic collisions to choose the most likely of two scenarios. 

This lesson relates to the NGSS Practices of Asking Questions (SP1) and Analyzing and Interpreting Data (SP6) because students pose questions that help drive their investigation. Students have to eliminate a scenario based on their calculations of velocity and momentum. Students also ask each other questions about their calculations, data, and analysis by questioning each other in small groups. 

The Warm-Up for this lesson is a quick five minute writing activity which I project using the interactive whiteboard at the front of the room. I have students write in their notebooks as many occupations that come to their minds that use physics in their daily routines. I choose this type of warm-up because within this lesson I ask students to take on the role of a local journalist and use physics models to determine which account is correct. Here is an example of student work

I want students to learn that applying physics involves more than solving an equation for an unknown or substituting values into equations. During this investigation, students ask questions to determine which scenario has the greatest likelihood of being an accurate account of the event in question.  Students communicate with each other using written, visual and verbal domains to give students with different learning affinities a time to shine within the project. The week-long project is broken up into several parts, with checkpoints built in for students to discuss their thought process with their lab mates in order to consider multiple viewpoints of the problem at hand. I assess students daily progress using a Habits of Work and Mind checklist

Using the Conservation of Momentum to Determine: "Which Collision is More Likely?"

45 minutes

After circulating the room to ensure that all of the student teams are familiar with a tech tool and create an initial visual, I introduce students to this week-long project. I give students a handout that they can use to identify the most likely scenario based on their data analysis. The handout has two eye-witness accounts of a collision that occurs between two individuals. One account treats the collision as an elastic collision while the other treats the collision as an inelastic collision. Both accounts define a set of physical attributes for each scenario.  During the first five minutes of this section, I distribute and discuss the expectations project with students including the visual and written components and peer editing process. After we discuss the expectations of the project, students spend 10-15 minutes completing the worksheet individually by hand.

Each group's facilitator ensures that all team members take turns explaining the evidence that they use to support their assertions on which scenario is the most likely of the two possibilities. Students then spend the next 10 minutes crafting an agreed-upon explanation for the most likely scenario. As students work on the project, I circulate asking questions and taking notes on my Classwork Assessment checklist to assess if students are effectively collaborating with their peers while trying to ascertain: "Which Scenario is Most Likely?" I use this assessment sheet for this section of the lesson to evaluate the effectiveness of each group in order to make changes to student teams if necessary.

After each student team identifies the most likely scenario, I ask for a representative from each group to present their data to their station mates. After each team presents their evidence, I ask questions about the best practices for comparing two claims, like creating a testable question and creating a physics experiment (SP4). Students spend a week working on this project with a lot of independent work outside of the classroom.

Using Technology to Investigate Momentum

20 minutes

In this section of the lesson, students use their understanding of the conservation of momentum for elastic and inelastic collisions to identify the velocity of both Troy and Sherry before and after a collision to decide which eyewitness account is the most plausible option to report. This part of the lesson is to help students learn that practicing physics is not simply about memorizing a set of equations identifying a model for a system. During this section of the lesson, I provide students with a prompt that reads “How is physics related to reporting the news?” This is the opening for students to work, in teams of 2-4, to determine: "Which Scenario Is More Likely within eye-witness reports of this lesson?" Over the next 20 minutes, students use technology of their choices (Popplet, PadletCoggle and Prezi) to create a visual that identifies which scenario is more likely using their current understanding of the conservation of momentum. I want students to apply the conservation of momentum to real-world scenarios to compare the validity of two possible eye witness' accounts. 

There are laptops and other means of digital technology throughout the classroom. I ask students to add images, links and equations that are related to investigating a crime to their visuals. After 20 minutes, I remind students to share the visual with the teacher and their elbow partners for later assessment. I ask students to create an initial visual which they modify as they learn more information and complete the project because I want students to learn that revision is one of the most important tools that scientists use when investigating the validity of a claim. This is a relatively quick brainstorming activity and is similar to mind mapping that I use in a different lesson. During this activity, I really want students to choose a digital tool that they are comfortable with to create multiple drafts of their presentations for this project. I use this type of visual because I want to give students an alternative to traditional lab reports and allows students to synthesize information from multiple sources into a multimedia project. In the next section, I ask students to identify ways that journalists use physics to accurately present the news using their experiences from today's lesson. Here is an example visual from this section of the lesson. 


10 minutes

At the end of this lesson, I ask students to respond to a writing prompt: "How do journalists use physics to help report accurate news?" in their notebooks. Student responses include, "Journalists have to check the facts by doing research and work with experts when reporting information that relates to physics like how fast a plane was traveling before it crashed", and "When reporting the news, journalist have to give credible information in a way that makes sense to the general public."  I use this type of closing question because I want students to make connections between the reasoning and mathematical logic we use in physics class and real world scenarios. 

To wrap up the lesson, I remind students to go over their daily progress with a math, science teacher or peer of their choice and to make sure teachers sign off on the lifeline checkbox and peers complete the peer edit sheets during the beginning of the next lesson. Students can meet with teachers and peers during our school's advisory sessions. I assess student progress each day for a week to determine if they have made adequate progress toward completing the project.