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# Introduction to Forces, Part 2 of 2

Lesson 2 of 12

## Objective: Students will utilize their understanding of forces to identify which object experiences a force and which object exerts a force during an interaction.

*75 minutes*

The goal of this lesson is to help students construct explanations about the forces acting on an object. This lesson addresses the HS-PS2-1, RST.11-12.4 and RST.11-12.7 standards because it asks students to conduct research and communicate ideas related to the net force acting on an object using a free body diagram model. It aligns with the NGSS Practices of Developing and Using Models, Using Mathematical Reasoning (SP5) and Constructing Explanations (SP6) for Science because students will use mathematical logic to create summaries to explain factors that are related to a forces acting on an object. This lesson also is aligned to the NGSS Cross-Cutting Idea of Patterns because students must create a visual model of the forces acting on an object given a written description of the physics of a system and recognize the magnitude and direction of the forces acting on an object from a written description of the forces within a system. I want students to learn that creating a visual model of the forces acting on an object is an essential skill for studying Newton's laws of motion. This relates to (SP6) because students have to leverage skills like note taking and considering multiple viewpoints to construct an explanation of forces acting on an object.

Students begin by taking notes in their lab notebooks using the information in an EdPuzzle which is a set of video notes with pause points embedded as green question marks. Students use the silent conversation strategy to have a whole class discussion on forces. Next, students work in small groups to create free body diagrams that correspond to the forces acting on an object. During the closure activity at the end of this lesson, I ask students to construct a definition to demonstrate an understanding of forces and free body diagrams. I assess student understanding throughout the lesson using informal check-ins and assess each student's work at the end of the school day.

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#### Bell-ringer

*10 min*

This portion of the lesson follows a routine to communicate the ideas that students need to be proficient in by the end of the semester and it also highlights the goals of the lesson to students. Students write the objective and additional piece of information in their notebooks as soon as they enter the classroom. 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 forces are interactions between two objects. Later on within this lesson I ask students to use information from an EDpuzzle to have a silent conversation with their classmates on the topic of forces. In this lesson, I want students to get ready to leverage information gathered from their understanding of vectors to construct free body diagrams models for forces acting on an object.

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#### EDpuzzle: Forces

*30 min*

During this lesson, I introduce a conceptual model for different types of forces and their relevance to different situations. 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 classifying different types of forces. 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 notebooks. I ask students if they have any questions or concerns about the methods discussed in the video. Then I follow up the EDpuzzle on forces with a strategy called silent conversations. The silent conversation strategy is a protocol which consists of:

- A visually stimulating artifact like an image, non-fictional text, or quote
- A call for silence
- A focus question
- The teacher asks students from each group to write noticings and wonderings silently on a large piece of chart paper
- After a short time, groups move to an additional station
- Students rotate to each station and repeat steps 4 & 5
- Silence is broken
- The teacher asks students to return to their original station and discuss the noticings and wonderings that their peers have written on the chart paper at their station
- The teacher asks share a summary of their discussion, either with the teacher or if time permits the entire class

During the silent conversation, I circulate and note that a few students attempt to break forces into component parts. This could be an artifact of our discussion on vectors.

During this section, I turn the "How are we learning arrow to Whole Class". I have a poster at the front of my room that has the title "How are we learning". It helps students learn the routines for successfully working in different types of learning configurations. When students are working independently I ask students to work silently remain on task and to raise their hands if they require help. When students are working on partner work, I ask that students take turns speaking and listening while working. During partner work students are to keep each other accountable and to keep their volume at a level where students who are more than 6 inches away from them would have trouble hearing their conversation. During team work, I ask students to respect the work and each other and to speak at a volume that students a foot away would have trouble hearing their conversations. During whole class activities, I ask that all students participate and sharing and listening to ideas. I use the designation AIH for activity in hand, this is helpful when students process information at different rates and gives everyone a heads up that multiple types of activities are going on in tandem.

During this section of the lesson, I distribute chart paper and markers to each table. Each piece of chart paper has a qualitative free body diagram and a focus question "How does this diagram connect to Physics?" taped to the center of it. I spend a minute or two I introducing this silent conversation strategy to my students, explaining that there is time later during the activity when we break the silence and work in pairs, but for now the expectation is that the room is silent. I also give students a minute to ask any questions. I then split the into groups and ask students to spend 5 minutes at each station silently writing both noticings and wonderings on the chart paper at that station. Students visit 3 stations in total, their original station plus two additional stations. There are six stations in total. I tell students to go to the next station after each five-minute interval passes.

After ten minutes, I turn the "How are we learning?" arrow to Team or Partners. Then I tell students to discuss and summarize the noticings and wonderings on the chart paper at their station on long sticky notes I provide each table. After five minutes elapse I ask for volunteers and give the highlights of their summaries to class and post the sticky notes on the interactive whiteboard at the front of the room. Some student responses include: "The diagram is simple to draw and shows the forces on an object," and "This image will help when solving a physics problem where I have to add the forces because I can add them like vectors." I choose this activity because I want students to consider multiple viewpoints as a way to extend their current knowledge of the way a model connects to a big picture view of forces in physics.

#### Resources

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After discussing "noticings" and "wonderings" about the silent conversation, I ask students to read about forces and free body diagrams. In this section of the lesson, I ask students to illustrate the forces acting on a system in a given scenario. I distribute a handout on forces and free body diagrams for students to complete in teams of two to four.

Student teams spend the next 20 minutes:

- Identifying the system
- Identifying the forces acting in each scenario
- Constructing a free body diagram for each system

As students are completing this task, I walk around checking in with them. The purpose of this assignment is to have students use information from multiple sources and perspectives, much like scientists construct explanations of forces acting on a single object within a system. Students spend 10 minutes discussing their solutions with their table mates.

During the last five minutes of this session, I collect the sheets to grade and return to students. Some of the sources include the reading from this previous lesson, notes, and our openStax digital textbook. This task helps students illustrate the depth of their current understanding of forces and free body diagrams.

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This closure asks students to identify and describe their personal level of understanding of key ideas within the lesson by crafting a free write on forces and free body diagrams. During the free write routine, students spend 5-10 minutes writing whatever comes to mind about today's lesson on forces and free body diagrams, without regard to grammar in an effort to make their current level of understanding of free body diagrams visible. Students write their responses to the closure activity in their notebooks. I like this activity because students identify and share the portions of the lesson students identify as important to understanding forces and representing forces using free body diagrams.

Student responses include: "When making a free body diagram it is important to know which interaction you are looking at, which object the force is exerted on and which object the force is exerted by", and "Remembering how to draw the normal force because it does not always point straight up the way gravity points downward". To wrap up this section of the lesson, I ask students to look at this tutorial and practice questions that I post on the class Edmodo wall for homework.

#### Resources

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- LESSON 1: Introduction to Forces, Part 1 of 2
- LESSON 2: Introduction to Forces, Part 2 of 2
- LESSON 3: Using Simulations to Investigate Forces
- LESSON 4: Free Body Diagrams
- LESSON 5: EDpuzzles: Forces, Fields and Other Exciting Things
- LESSON 6: Newton's First Law
- LESSON 7: Newton's Second Law
- LESSON 8: Applying A Problem-Solving Protocol to Newton's Second Law Problems
- LESSON 9: Newton's Third Law
- LESSON 10: Applying A Problem-Solving Protocol to Newton's Third Law Problems
- LESSON 11: Creating A Visual on Forces and Newton's Laws
- LESSON 12: Understanding Check: Forces and Newton's Laws