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# Newton's Laws Review

Lesson 15 of 16

## Objective: Students will be able to solve and explain problems involving Newton's Laws.

*55 minutes*

As our unit on Newton's Laws comes to an end, this lesson is meant to provide students a comprehensive review before they take the unit exam. The class starts with students solving a ranking task and a discussion of the solution. Then, students use their computational thinking skills (SP 4-6) to collaboratively solve and share problems involving net force, friction, mass, and acceleration (HS-PS2-1). After students are finished working through their problems and sharing the solutions, the class ends with a twitter closure.

Materials needed for this lesson: 1 notecard per student.

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Because this lesson is a cumulative review before tomorrow's test, today's introduction provides students a chance to self assess their comfort level. When students walk into the room the force difference ranking task is already projected onto the screen at the front of the room and there is a copy of the handout for each student. I pick this ranking task in particular because it is a question related to Newton's Third Law, and the rest of the class hour will be spent reviewing Newton's First and Second laws.

Once the students are settled, I read the instructions from the top of the activity. My reading of the instructions is to ensure students understand that class has started. I emphasize to students that they should work individually and take about five minutes to rank the graphs, explain their reasoning, and then assess their level of confidence. During these five minutes of work time, I walk around the room and informally assess how students are doing with simple glances at their work. My changes in location help students stay quiet and focused.

When the five minutes are over, I reveal the answers to the students by writing that all force differences are the same onto the front screen. I then ask if anyone knew and was confident in the idea that each situation has the same force difference. Since my students are fabulous, inevitably there is at least one who did and is willing to admit it. It's that student that I then ask to explain his reasoning. If the explanation is complete and clear, I commend the student! In the event the explanation needs to be expanded, I contribute any missing information so the whole class has a complete understanding of the material. Regardless, I end the introductory activity by reminding students that conceptual questions like these are an important component for success on the unit and AP Physics 1 tests.

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Today's class will use collaborative problem solving as a way for students to review forces. Students are each given a different problem from a review problem set. These problems are taken from our textbook and are problems that I feel are most representative of the test questions. Students stay at their lab tables for this activity so we don't lose time while they get into groups and I give each group one of the problems with its final answer. The problem that each group receives is random: I literally walk down the center aisle and give the group whichever problem is on the top stack of my pile because all of the students should be able to answer any of these questions.

I've also included the answer with each problem (not the solution, but simply the numerical answer with units). The purpose in doing this is that I want students to worry less about getting the correct answer and more about their ability to prove and justify that answer. The AP Physics 1 exam places great emphasis on justifying answers, so I want students to have an opportunity to orally practice the justification process.

My expectation is that students take about fifteen minutes and actively work together to write down the solution on the paper I pass out to them. Without giving students too many details, I tell them to be prepared to not only show their solutions, but to also be able to *explain* their solutions. Also, I encourage students to use pen as they work. Using pen keeps them from erasing, so even if they make a mistake or change their thinking I can see evidence of their entire thought and solution process.

As students are working at their lab tables, I walk around and ensure that everyone is engaged in the discussion and thinking critically about their assigned problem. I am willing to give students hints as I observe, but my feeling is that by this point in the Newton's Laws Unit students should be able to independently work through these problems. If a group happens to finish early, they can either help a group seated near them work through their problem or have time to individually review and prepare for the unit exam.

#### Resources

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#### Students Share Solutions

*25 min*

After the collaborative work time is over, I ask students to present their solutions to the rest of the class. Each group comes forward, puts their problem with the solution under the document camera, and explains their solution to the rest of the class. The goal of this activity is to show students the variety of problems that will be on the unit exam.

Because my students are sometimes shy, I ask if any groups volunteer to go first. There is always at least one group that wants to get the presentation out of the way, so I choose them and applaud them for being so willing. This first group of students walk to the front of the room and place the problem with solution under the document camera. One person from the group must read the problem aloud so the entire class becomes familiar with that problem, as they have not seen it before. A second student should explain any diagrams that were drawn and the list of given information. Finally, a third student from the group will verbalize the solution that has been written on the paper.

Once the solution is appropriately provided (I wrote the answer in pencil and the students wrote the solution in pen), I ask the class if they have any questions for the group. If someone from the class does need to ask a clarifying question, or if I need to ask a clarifying question throughout the solution sharing, I expect that any presenting group members who haven't participated yet will answer these questions.

Once that first group is finished, I let them pick which group they'd like to see share next. This chosen group comes forward with their problem and solution, shares, and appropriately answers questions as the last group did. The process repeats itself until all problems have been shared. If students took good notes throughout this activity, they now have a great study resource of new questions with solutions.

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#### Twitter Question Closure

*5 min*

As closure today, each student will get an index card. As I pass out the index cards, I direct students to write a last moment question on that card. My goal in this activity is to give students an opportunity to ask one more question about forces before the unit exam. I let students know that students I will be posting their questions and my answer through my Twitter account throughout the day. All students get to see each question and answer this way: it's a fun supplemental review method for the students while they are out of class.

Students are welcome to discuss ideas and talk while coming up with their final question. Although it's not mandatory that each student write a question, I strongly encourage participation. I give students about 90 seconds of work time before I start walking around and collecting the cards. As I collect the cards I check in with each group, ask them how they are feeling about forces, and if they are ready for the test on Monday. It's a great way for me to connect with as many individual students as possible before they leave for the day.

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- LESSON 1: Defining Force
- LESSON 2: Forces as Vectors
- LESSON 3: An Introduction to Free Body Diagrams
- LESSON 4: Newton's First Law
- LESSON 5: Newton's Second Law in 1-D
- LESSON 6: Newton's Second Law in 2-D
- LESSON 7: Ramping up Forces
- LESSON 8: Practicing Newton's Second Law
- LESSON 9: Tensions, Pulleys, & Elevators - Oh My!
- LESSON 10: Tension Lab
- LESSON 11: Figuring out Friction
- LESSON 12: Newton's Third Law
- LESSON 13: An Atwood's Machine Inquiry Lab
- LESSON 14: Newton's Laws AP Practice
- LESSON 15: Newton's Laws Review
- LESSON 16: Forces Unit Test