An Introduction to Momentum

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Students will be able to define momentum in terms of mass and velocity.

Big Idea

Students use 3 different websites to explore the definition of momentum.


This is the first lesson in our linear momentum unit, so students work with a clean slate today. My goal is to introduce the concept of linear momentum, and class starts with a video introduction. Then, students explore different websites to define momentum (HS-PS2-2), before class ends with collaborative problem solving (SP5 & SP8).

Video Introduction

10 minutes

As soon as students come into the room and are seated, I play this video on momentum in sports. I choose this video because many of my students play or watch sports, so it's my hope that the video connects momentum to something they are passionate about. After the video has finished, I ask students to consider if they've experienced momentum in their lives. The goal of my question is to have an informal discussion about momentum so that students become familiar and comfortable with using the word momentum.  

I allow the discussion to continue for about 5 minutes, as my students are eager to share stories about momentum shifts they see or experience in different games. I allow anyone to share, since I continuously strive for a fair and welcoming classroom. When there is a lull in the conversation, I ask students to think about what momentum might mean in physics. Without providing them the answer, I let that question hang there and use it as a way to pique my students' interest before moving into the next activity.

Website Reviews of Momentum

20 minutes

Now that students are thinking about the idea of momentum, I ask them to get into groups of three. My class is so familiar with each other at this point in the year, that I have no worries about them choosing their own groups. I also give each student a notecard and ask them to select the number 1, 2, or 3. 

Once students all have a notecard and choose a number within their groups, I explain today's activity. Each student will get a computer from the front of the room (students are already familiar with how to do this) and explore a website about momentum. The student that is assigned number 1 explores the Physics Classroom's explanation of momentum. Student number 2 explores PhysicsLAB's explanation of momentum, and student number 3 reads hyperphysics' momentum explanation.

After students have read their respective momentum explanations, they write the quantitative and qualitative definition of momentum on their cards along with one example. The students work individually as they read and write, but because they are in their groups of 3 the activity isn't completely silent. I encourage students to discuss topics from the reading or questions that arise as they work through the assignment. The goal is that each student ends the activity with a notecard that can be used a resource during the collaborative problem solving portion of the lesson.

Collaborative Problem Solving

20 minutes

Students remain with their trios from the website review activity as I pass out a copy of the homework to each student. This is an assignment that needs to be completed by each individual on a separate sheet of paper, although they may use their partners (and notecards) as a resource while working in class. Students use their peers to compare answers and discuss strategies to solve the problems. Their notecards are also helpful, since the cards remind students of the momentum equation and how the equation is used in an example problem.

As closure and an informal summative assessment, students have the rest of the class to start tonight's momentum homework. The assessment is summative as it includes use of kinematics concepts that were learned earlier in the school year. I call it informal because I don't want students to get nervous that it counts as a quiz or test grade. Since my goal is to assess their level of understanding of momentum, I collect and grade the assignment for accuracy at the start of the next class meeting. Not only do I want to give students personalized feedback on this homework assignment, I also want to check the pacing of the course and make sure my students are ready to move on to the next lesson.

This is our closure activity for today and it's meant to have students apply their newly learned knowledge. I am also trying to take a step towards a flipped classroom. I like students to have me as a resource when they work through problems, and I think it helps them build confidence. In the past I've attempted to do entire class periods of a full flipped classroom, but it's hard to hold the students accountable for digesting the needed material. I find that a combination of work time (that lasts right up until the bell rings) and in-class learning best fits the needs of my students.