Newton's Second Law and Free Body Diagrams, Part 2

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Objective

Students will be able to identify when an object has a net force and take the net force and solve for acceleration or mass.

Big Idea

Students apply Newton's Second Law to various situations.

Jigsaw Elevator WS Answers

20 minutes

The goal of this lesson is for students to apply the ideas of free body diagrams and Newton's Second Law to various types of problems that require more than one step to solve. It builds on HS-PS2-1 in that students investigate, develop, and apply Newton's second law. These problems are an extension of those that students completed earlier in the unit that students needed more preparation for. This lesson forces students to use the models that they have developed (SP2) with free body diagrams and then use that information to solve for mass or acceleration using a mathematical formula for Newton's Second Law (SP5). When going through the problems, students will explain their thought process to other students when solving the problems (SP6).

To start out the lesson, I have students take out the Stages of an Elevator WS that they completed in class on the previous day with groups. Since we did the first two together, I ask each group member to be in charge of a problem to complete a jigsaw to check work with other groups in the classroom. Each table has seats labeled #1-4 so I have all of the #1s meet in the back to discuss the 3rd situation, #2s to discuss the 4th situation, #3s to discuss the 5th situation and #6s to discuss the last situation. I ask groups to call me over when everyone in the group has reached a consensus to make sure that they have the correct answer before they move back to their home groups. I give them about 5 minutes to confer with their jigsaw groups.

After each jigsaw group has checked with me, I have students move back to their home groups to discuss their answers. I give them about 10 minutes to discuss. After all group members are done, I ask students if they have any questions before moving on to completing the next worksheet.

FBD and Net Force Worksheet #2

40 minutes

To complete the Free Body Diagram and Net Force WS #2, I have students work with their partner sitting next to them. I like for them to work with someone from their table because they will be eventually creating whiteboards and presenting to the class about the problems so I want them to be comfortable with solving the problems with their group. This worksheet focuses more on the application of Newton's Second Law and using free body diagrams in solving the problem in multiple steps.

I give them about 35 minutes to work on this worksheet since the problems require more thought than previous problems. The students work with their partners to complete each of the problems and I tell students to draw a free body diagram for each problem to help them. As students work, I walk around to make sure they are on task. To end class, I ask students to be prepared to whiteboard the answers to these problems during the next class.