1.4 — Motion: Playing Catch – Part III

App Features

Using the motion lens students will:

• Use previously recorded performances.
• Open the graph drawer.
• Add high and low speed stickers.

Expected Activity Time

• Total Activity Time: 45 minutes
• Introduction: 15 minutes
• Activity: 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: Motion: Playing Catch 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 motion.
• Remind students that in the last lesson they learned to describe the motion of an object by referencing the speed of the object, the distance it traveled (vertically, horizontally and along the path of motion), and the direction of motion. Tell students that today they are going to build on those skills by learning to read the graphs that the Playground Physics App creates.
• Project the “Graphing Motion” 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. This worksheet introduces the concept of velocity to the students. Since the app doesn’t specify what the direction is called, you will want to discuss with your class how you will interpret the arrow when writing velocity. You might want to say an object is moving right or left, east or west, or just use arrows to indicate the direction as the app does.

Investigation: 20 minutes

• Tell students that they are going to look for patterns in the same video they used in the last lesson. Provide 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.
• Have students pull up the video of two students playing catch that they used for the last lesson. The path of motion for the ball 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 throws of the ball. Because the lesson looks for patterns in motion, students will not see this unless they have tracked the path of motion for multiple throws of the ball back and forth between the two people 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 ball was moving the fastest and place a box around the places where the ball was moving the slowest. The graph of motion should be cyclical with the speed increasing and decreasing each time the ball moves back and forth.
• Have students place high and low speed stickers on the places in the video where the speed is at the highest and lowest. How many stickers are appropriate to place on the video will depend on how many times the students threw the ball back and forth.
• Have students describe what is happening when the ball is moving the fastest, what is happening when the ball is moving the slowest, and the overall patterns in the motion of the ball.
• Have students use their observations to complete the “Patterns of Motion” 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: Graphing Motion

1. 
2. 3.6 m
3. 7.8 mps
4. 7.8 mps right/E/→
   (Since the app doesn’t specify what the direction is called, you will want to discuss with your class how you will interpret the arrow when writing velocity.)

Answer Key: Patterns of Motion

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 motion of the ball that your students may notice while playing catch.
   • The path of the ball always forms an arc (parabola) between the person throwing the ball and the person receiving the ball.
   • The vertical speed of the ball will be the slowest at the top of the arc and faster on each side (when thrown and caught).
   • The horizontal speed of the ball will be fastest when it is first released from the hand of the person throwing it.

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