Modeling Momentum Using Graphs
Lesson 8 of 14
Objective: Students will use graphs to analyze the momentum before and after a collision.
The goal of this lesson is to help students use graphs to construct explanations for concepts that relate to momentum. This lesson comes after a series of lessons where students construct an explanation of momentum and use close reading strategies to stretch their understanding of momentum. This lesson addresses the RST.11-12.3 and HS-PS2-2 standards because it asks students to obtain information from the second Minds on Physics activity on momentum and collisions. It aligns with the NGSS Practices of Developing and Using Models (SP2), Analyzing and Interpreting Data (SP4), and Using Constructing Explanations for Science (SP6) because students will use their prior knowledge of the conservation of momentum in a closed system to interpret graphs and determine information that relates to the momentum of objects that collide.
Within this lesson students use graphical data to determine information about objects before and after a collision. Students use a handout to construct the initial and final conditions of objects that collide. Students then use their review understanding of momentum to complete a Minds on Physics module. Finally, students create headlines that correspond to today's lesson. Within this lesson I ask students to focus on deepening their current understanding of momentum, its conservation and impulse. I assess student understanding throughout the lesson using informal check-ins and assess each student's work at the end of the school day on a scale of 1 (Advanced Beginner) to 5 (Highly Proficient).
At the beginning of each lesson, I have a quick Bell-ringer to get students focused on the tasks for today's lesson. There is a slide with the date, the objective and an additional prompt projected on the interactive whiteboard with a red label that says "COPY THIS" in the top left-hand corner. Sometimes the additional prompt is a BIG IDEA for the lesson or the Quote of the Day or a Quick Fact from current events that is related to the lesson. The red label helps my students easily interact with the information as soon as they enter the room and avoids losing transition time as students enter the classroom.
Today's Big Idea is that interpreting graphical data that represents a system before and after a collision is a great way to learn about momentum and impulse. I choose this Big Idea because students often get caught up in the idea of that obtaining data is more important than interpreting data and often do not focus on analyzing. I want students to consider multiple ways to represent data, not just on the numerical solution to a word problem that most students associate with physics.
During the first five minutes of this section of the lesson, I distribute this handout and ask students to read the instructions silently to themselves. This handout gives students a conceptual model for the conservation of momentum in a system, then asks students to list the objects in the system and to represent the momentum of the objects in the system using horizontal bar graphs. After five minutes pass, we discuss models for momentum and impulse. I spend a minute or two asking students to use this opportunity to make connections between mathematical models and graphical models of momentum, its conservation, and impulse. I choose to use this worksheet because I believe that multifaceted models are more likely to be remembered and understood by students. I ask students to spend the next thirty minutes working on this activity individually.
While students complete the activity based on the information from their notes, I circulate the room and address students concerns as they arise. After thirty minutes pass, I ask students to spend ten minutes discussing their solutions with the students at their lab tables and to make any corrections they would like based on those discussions before I collect the worksheets.
During the last few minutes of this lesson, I collect the worksheets and ask students from around the room to identify puzzles that relate to the problems from this section of the lesson. Click here to see an example of student work.
In this section of the lesson, I ask students to share their answers to the question "How would you use your understanding of momentum to determine the final velocity of an object involved in a collision?" During the first five minutes of this portion of the lesson, I give students a focus question to analyze in their notebooks. First students write their answers in their notebooks and then they share their answers with their station partners.
At the end of five minutes, I call on a representative from each table to share his or her answers with the class. This part of the lesson focuses on activating prior knowledge and help students make connections between various concepts we have covered so far in the semester. Some student responses include, "If the two objects bounce off each other, I can use the elastic collision model for the conservation of energy and solve for the final velocity that way", and "If I know the initial velocities and masses of the objects involved, I can find the final velocity using an equation for the conservation of energy."
During the next five minutes, I distribute Chromebooks and ask students to go to the Minds on Physics link that I post on our class Edmodo wall and complete assignment 2 on momentum and collisions. Then I ask students spend 12-15 minutes using the information from this lesson along with other information from this unit and the Physics Classroom website to review for an upcoming understanding check on momentum and its conservation. I want students to have a chance to clear up any misconceptions before attempting to demonstrate understanding on an assessment I provide later this week.
During the closing activity, I ask students to spend five to ten minutes creating headlines that represent the most important parts of today's lesson. Students complete the exit slip by writing in their notebooks or by posting them on our Edmodo wall using the private post option. I choose this type of activity because I want to give students a way to give voice to their thoughts on momentum in a low pressure manner.
Some student responses include, "Drawing bar graphs of an object's momentum before and after a collision makes it easy to see that the total momentum is constant in a system", and "Studying momentum with a partner helped me improve my Minds on Physics score." To wrap up the lesson, I ask students to study for the upcoming understanding check on momentum and its conservation.