3.4 — Energy: Swinging – Part III

App Features

Using the energy lens students will:

• Use previously recorded performances.
• Open the graph drawer.
• Add kinetic and potential energy stickers.

Expected Activity Time

• Total Activity Time: 45 minutes
• Introduction: 15 minutes
• Investigation: 20 minutes
• Discussion: 10 minutes

Materials and Prep

• iPad with the Playground Physics app
• Videos created by students in the app
• Projector with iPad adaptor
• Worksheet: Energy: Swinging – Part III

Activity

Introduction: 15 minutes

• Tell students that when scientists study the world they look for trends or patterns in natural phenomena. These patterns are things that happen consistently because they are controlled by the physical properties of Earth. Tell students that today they are going to be physicists and look for the patterns in energy.
• Remind students that in the last lesson they learned about kinetic and potential energy. Tell students that they are going to build on those skills by learning about kinetic and potential energy in relation to speed using the graphs that the Playground Physics app creates.
• Project the “Thinking About Graphs” portion of the worksheet and have students follow along on their own copies. This worksheet is intended to help students learn to read the graphs in the app. Work through the worksheet as a class.

Investigation: 20 minutes

• Tell students that they are going to look for patterns in the same video they used in the last lesson. Pass out iPads to groups of students. To access the videos their group recorded initially, students should work in the same group and should use the same iPad as in previous lessons. Use the groups sheet provided in the “Getting Started” section to help keep track of this.
• Have students pull up the video of someone in their group swinging that they used for the last lesson. The path of motion for the person swinging should still be marked on the video so they won’t need to re-annotate the video. Make sure that students have annotated the path of motion for multiple full swings (back and forth). Because the lesson looks for patterns in energy, students will not see this unless they have tracked the path of motion for multiple passes back and forth of the swing in the video.
• Have students open the graph drawer so they can see the graph “along path” of the motion in the video and draw the graph for speed on the space in the worksheet.
• Have students circle the places on the graph where the person was moving the fastest and place a box around the places where the person was moving the slowest. 
• The graph of person should be cyclical with the speed increasing and decreasing each time the swings back and forth.
• Have students place kinetic and potential energy stickers in the video. How many stickers are appropriate to place on the video will depend on how many times the person in the video swings back and forth.
• Have students describe what is happening when the person is moving the fastest, what is happening when the person is moving the slowest, when the person is the furthest from the ground, and the overall patterns that exist in the energy in association with the speed of the person who is swinging.
• Have students use their observations to complete the “Patterns in Energy” portion of the worksheet together in their groups.

Discussion: 10 minutes

• Have the class come back together and have each group share the patterns they noted in the investigation.
• If there are discrepancies in the patterns, discuss as a class what could cause the differences groups saw in their patterns. Ask the class if everyone should have the same patterns. Have students share their reasons for why or why not.
• Remember to check the Parking Lot of questions at the end of the class period. Remove any questions that have been answered and add any new questions that may have come up.

Answer Key

Thinking about Graphs

1. 
2. At this point, the rocket is traveling fast because it was just launched. The rocket still has a high level of kinetic energy as a result of the force of the air that caused the rocket to launch.
3. The potential energy is increasing at this point because the height of the rocket from the ground is increasing.

Patterns in energy

1. Answers will vary.
2. Answers will vary.
3. Answers will vary.
4. Answers will vary.
5. Answers will vary.
6. Answers will vary.
7. Below are some of the overall patterns in the forces on a person jumping rope that your students may notice.
   • The potential energy of the person swinging increases as they get further from the ground.
   • The potential energy of the person swinging is at a maximum when the person is furthest from the ground.
   • Kinetic energy increases as the speed of the swinger increases.
   • The kinetic energy of the swinger is at a maximum when the person is moving the fastest. This happens at the bottom or apex of the arch of motion of the swing.

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