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# Bumper Car Physics

Lesson 7 of 14

## Objective: Students will demonstrate their understanding of the conservation of momentum by creating a visual using bumper cars to model an elastic collision.

## Big Idea: Bumper cars are useful models for studying the conservation of momentum and elastic collisions.

*75 minutes*

The goal of this lesson is to help students use their prior knowledge of bumper cars to construct an understanding of the conservation of momentum and collisions. At this point in the semester, students have crafted explanations for key momentum terms using graphic organizers, solved momentum related problems using a protocol, used close reading to deepen their understanding of impulse and momentum, and investigated the conservation of momentum using a hands-on lab activity. With this in mind, I thought it would be a good idea to give students another way to construct an understanding of the conservation of momentum using bumper cars as a model. This lesson addresses the HSA.REI.A.1 and HS-PS2-2 standards because it asks students to solve for the velocity of two cars after a collision using their understanding of the conservation of momentum. It aligns with the NGSS Practices of Planning and Carrying Out Investigations (SP3), Analyzing and Interpreting Data (SP4), and Obtaining, Evaluating and Communicating Information (SP8) for Science, because students use their prior knowledge of the behavior of bumper cars to model the conservation of momentum during an elastic collision.

Within this lesson, students construct an understanding of elastic collisions using an EDpuzzle. Students discuss ways to find two unknown velocities during an elastic collision. Students then use a visual to illustrate their current level of understanding of elastic collisions. Finally, students create headlines that correspond to today's lesson. Within this lesson, I ask students to apply their current understanding of momentum to a real-world problem. 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).

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#### Bell-ringer and Warm-Up

*15 min*

During this portion of the lesson, students complete a routine where they write the objective and an additional piece of information in their notebooks. I project a slide with the date, the objective and an additional prompt 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 additional piece of information is a BIG IDEA which states that bumper cars are useful models for studying the conservation of momentum and elastic collisions. Later on in this lesson, I ask students to use the information they gather from an interactive activity and our digital textbook to create an infographic on the conservation of momentum. In this lesson, I want students to get ready to use their experience successfully working in teams, and gathering evidence to demonstrate an understanding of the conservation of momentum.

After students complete the bell-ringer activity, I ask students to complete a free-write in their notebooks using the guiding question "What happens when two bumper cars collide?" A free write is a strategy where students write on a single topic for a set amount of time, without regard to structure or grammar. Some students draw mind maps while others write short paragraphs or sketch images. Click here to see an example. Student responses include, "Both cars bounce off of each other", "You can get stuck in a corner", and "The drivers jerk forward and then try to hit each other again."

After ten minutes pass, we have a short five-minute discussion on students answers to the guiding question and connections between the guiding question and physics from our unit. During our discussion, I inform students that in physics we call collisions where momentum and kinetic energy are conserved and objects bounce off of each other elastic collisions. In contrast, I tell students that collisions where kinetic energy is not conserved and objects tend to stick together are called inelastic collisions. During the next section of the lesson, students watch an EDpuzzle on elastic collisions that they use to create a visual on bumper car physics.

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#### EDpuzzle: Elastic Collisions

*15 min*

During this lesson, I introduce a conceptual model for the conservation of momentum during elastic collisions. I include a set of notes that I project at the interactive whiteboard in the front of the room. This part of the lesson focuses on applying a mathematical model to a word problem that relates to an elastic collision. For the first ten minutes, I play the video at the front of the room for the entire class and pause at the pause points I have embedded as green question marks in the video.

During this ten-minute period, students take notes in their lab notebooks. I ask students if they have any questions or concerns about the methods discussed in the video. Some student responses include, "What does he mean by energy is lost in the real world?", and "Will we look at another example where energy is lost?". Later on in this lesson, students will create a visual on elastic collisions using bumper cars as a model.

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#### Elastic Collision Visual

*40 min*

During this section of the lesson, students first spend the first five minutes choosing a partner and identifying one of these presentation options:

to create a visual on "The Physics of Bumper Cars".

The minimum components of each visual are given below:

1. Backstory: Give the audience the backstory (what’s the significance of the problem)

2. Physics of the Problem (P.o.P.): Give a Quick overview of the problem

3. Solution: Step by Step solution including a description of each step, with equations, units and an actual solution with explanation

4. Framework: Explain the connections between the physical concepts in your solution

5. Tips: Give tips on how to solve similar problems in the future

After students choose a partner, the pair spends the next 15 minutes working in pairs completing this activity. During this activity, students gather data using an interactive activity to determine whether momentum is conserved or not during an elastic collision. First students determine the of two cars before and after a collision if one car is initially at rest. Then students determine the momentum of cars within a system if one is initially moving slower than the other car that with which it eventually collides.

Next student pairs spend about 20 minutes working in pairs use information from the Physics Classroom website, our digital textbook and class notes to create a visual on bumper car physics. I remind students to use their six-inch voices while working with a partner so that other students who are more than six inches away are not influenced by their discussion. After students complete their visuals we discuss their thoughts on the activity for a minute or two. Then I collect the visuals to grade and return to students. Some student comments include, "This is more complicated than the simulation lab" and "Why is there only kinetic energy in the equation if the total energy is conserved?"

#### Resources

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#### Closure

*5 min*

The closure activity asks students to create headlines about the portions of this lesson they think are the most important or challenging. Student responses include: "Elastic collisions are harder to understand than I thought", and "Simulations of perfectly elastic collisions are easier to understand than bumper cars". This type of closure activity asks students to summarize their thoughts on their current level of understanding of elastic collisions based on today's lesson.

To wrap up this section of the lesson, I ask students to look at the Minds on Physics assignment #7 on momentum and collisions that I post on the class Edmodo wall. I also ask students who did not complete their visuals in class to share their visuals with me by midnight on Thursday.

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- LESSON 1: Introduction to Momentum: Using A Graphic Organizer to Construct an Explanation
- LESSON 2: Constructing an Explanation of Momentum
- LESSON 3: Applying a Problem-Solving Protocol to Momentum Problems
- LESSON 4: Creating A User Guide To Solve Basic Momentum Problems
- LESSON 5: Practice Problems: Impulse
- LESSON 6: Modeling The Conservation of Momentum
- LESSON 7: Bumper Car Physics
- LESSON 8: Modeling Momentum Using Graphs
- LESSON 9: Using The Conservation of Momentum to Decipher Fact from Fiction
- LESSON 10: Challenge Problems: Momentum and Collisions
- LESSON 11: Traffic Violations
- LESSON 12: Comparing Kinetic Energy and Momentum
- LESSON 13: Momentum and Its Conservation: Understanding Check
- LESSON 14: Crafting A Prototype to Protect An Egg During Freefall