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**Grades:** 5-8

**Author:** Adrienne Studd

**Source:** Balloon Ball from: "That's the Way the Ball Bounces" written by Sandra Van Natta and Sue Hall for the Polymer Ambassadors http://www.polymerambassadors.org

In this activity, students will realize that different sports use balls with different amounts of rebound. Understanding this idea, the students will determine if the number of balloons in a balloon ball affect the rebound height. The students will then use the ball to discuss energy conversions.

**What should students know as a result of this lesson?**

- Students will describe the energy conversions (potential and kinetic) as the balloon ball falls and rebounds
- Students will describe why a ball rebounds
- Students will explain the Law of Conservation of Energy
- Students will analyze how the number of balloons in a balloon ball impacts the rebound of the ball

**What should the students be able to do as a result of this lesson?**

- Students should be able to use the experimental design process to investigate the energy conversions and the rebound of a student-made balloon ball. Through the activity, the students should also be able to identify variables, collect data, and create an accurate graph of data and draw conclusions from the data.

- Meter stick
- 10-12 round balloons per group
- Scissors
- Websites for background information on bouncing balls and different sport balls as needed
- Computer/projector to show the websites

**Engagement**

Use the following websites and their images to conduct a discussion about sports and the type of ball used. For example, ask the students why a tennis ball is not used in baseball games or why a ping-pong ball is not used in golf. (The balls are designed based upon the requirements of the sport and the rebound of the ball. A tennis ball would go too far in baseball and would not provide much challenge for the team on offense. On the other hand, a ping-pong ball does not have the same amount of rebound as a golf ball and would not travel the required distance when playing golf.) Ask the students to provide additional examples.

http://www.exploratorium.edu/baseball/bouncing_balls.html

http://www.exploratorium.edu/sports/ball_bounces/ballbounces3.html

Tell students their challenge: As a group you will have 10-12 balloons (based upon teacher choice) to make a balloon ball. You are designing a ball for a sport that needs the greatest possible rebound when dropped from a height of 1.0 meter.

*Assessment:* Monitor the students' understanding of the need for a specialized ball in sports by asking the students to provide additional examples. (whiffle ball vs. baseball, bowling ball vs. basketball)

Before proceeding, be sure that students understand the challenge by asking one or two students to explain the challenge in their own words to the class. Correct any misunderstandings.

**Exploration**

Divide the students into groups of three. The job assignments could be the release person, distance observer and the recorder. All students should assist in the creation of the balloon ball. The students should decide how many balloons to use in their balloon ball. However, they will need to test at least three different balls. For example, students might want to make a ball with 3 balloons and then perform the test. Next they could add balloons to the ball to make a ball with 7 balloons and then perform the test. Finally, they could add balloons to make a 10-balloon ball and then perform the test. It may be helpful to show students our video demonstration of the procedure. During the tests, the students should record their data in a data table. (Number of balloons in the ball and the height of the first rebound.) Remind students to conduct each test at least three times. Once all data have been collected, graph the results of the three trials. Find the average and the mode for each trial. Make a bar graph using the data.

*To make the balloon ball:

- Blow up a round balloon and tie it off so that it is slightly smaller than a fist.
- Using a second balloon, cut it with scissors at the neck.
- Open the balloon and place the blown up balloon inside.
- Rotate the direction of the balloon ball and place another cut balloon around the balloon ball.
- Repeat steps until the balloon ball has the desired number of balloons.

*Assessment:* Monitor the students' work and adherence to the safety procedures. Check to see that all of the students are following the procedures, making accurate observations, and recording the data accurately using the metric system.

**Explanation**

Share the data and graph with the class. After the students have answered the following lab questions in their groups, discuss the questions as a class.

- Based on your data, what is the best number of balloons to use for a super bouncy ball?
- Why do you think this number of balloons make the ball bounce better?
- What is your definition of rebound?

Once the students have shared data and discussed the questions, students should describe the forces and energy conversions that are taking place in the balloon ball. When the ball is dropped, the ball's energy is gravitational potential energy (GPE). The force of gravity causes the ball to fall towards the ground. During the fall, the ball's GPE is being converted into kinetic energy (KE). At the moment the ball hits the ground it momentarily stops. The KE has decreased and Elastic Potential Energy has increased to its maximum. Eventually the ball returns to its original shape and bounces back upward. The Elastic Potential Energy changes into KE. As the height of the ball increases, the KE changes into GPE. The rebound height of the ball will never be as tall as the drop height of one meter because some of the energy in this system becomes heat and sound energy. As more of the energy is changed to heat and sound, the ball will eventually come to a stop.

Ask the students to draw the balloon ball and label the gravitational potential energy (GPE), the elastic potential energy (EPE), the kinetic energy (KE) and any other forms of energy or energy conversions observed during the trials.

*Assessment:* Determine the students' understanding of their data and rebound by asking and discussing the lab questions.

- Based on your data, what is the best number of balloons to use for a super bouncy ball?
- Why do you think this number of balloons make the ball bounce better?
- What is your definition of rebound? (to attempt to return to the starting position)
- Ask the students to draw the bouncing balloon ball and label the gravitational potential energy (GPE), the elastic potential energy (EPE), the kinetic energy (KE) and any other forms of energy or energy conversions observed during the trials. (Before the ball is dropped (GPE) During the fall and rebound (KE) At impact (EPE, Sound, heat))

**Elaboration**

Ask the students to evaluate and predict:

- What do you think would happen in the balloon ball bounce if 100 balloons were used in the ball?
- What do you think would happen if the initial drop height were 2.0 meters?
- What do you think would happen if a balloon ball was made from Mylar?
- What do you think would happen if the medium inside the first balloon was changed from air to helium or water?

Discuss the questions and answers as a class. Share ideas and possibly create a test to find the answer to one of the questions.

Remind the students that in sports, the ball is specially designed for the rules of the sport. Brainstorm some games that might benefit from the newly constructed balloon ball with the greatest rebound.

Show the students the video clip of a bouncing basketball. Ask the students to draw the basketball at its highest point, when it is falling, when it is at its lowest point, when it is rebounding, and when it is at its highest rebound height. Label the energy conversions taking place in each picture. Identify the pictures with the greatest potential energy and the greatest kinetic energy.

*Assessment:* Use the remaining lab questions to determine the students' understanding rebound, energy conversions, and the interpretation of data. Review and re-teach any misconceptions

- What do you think would happen in the balloon ball bounce if 100 balloons were used in the ball? (students should use their own data to make a prediction)
- What do you think would happen if the initial drop height were 2.0 meters? (students should use their own data to make a prediction)
- What do you think would happen if a balloon ball was made from Mylar? (Mylar is the common shiny or silver helium balloons. Mylar is not elastic, this would not work. Check to see that the students understand that the type of material influences the rebound height.)
- What do you think would happen if the medium inside the first balloon was changed from air to helium or water? (accept all reasonable answers)

Show the students a video clip of a bouncing basketball. Ask the students to draw the basketball at its highest point, when it is falling, when it is at its lowest point, when it is rebounding, and when it is at its highest rebound height. Label the energy conversions taking place in each picture. Identify the pictures with the greatest potential energy and the greatest kinetic energy. (highest point = greatest GPE, falling = GPE to KE, hitting the ground = KE to Elastic Potential, Sound, and heat, rebound = PE to KE)

- Students should have previously discussed potential/kinetic energy and energy conversions during class.
- Students should be able to measure accurately using metric measurements.
- Students should be able to calculate averages and find the mode of a data set.
- Students should be able to create a bar graph.

- Learning Cycle
- Hands-on/Minds-on Learning
- Inquiry
- Discussion
- Probing Questions

**NGSS Standards:**

- MS-PS2-2 Plan an investigation to provide evidence that the change in an object's motion depends on the sum of the forces on the object and the mass of the object.
- MS-PS3-1 Construct and interpret graphical displays of data to describe the relationships of kinetic energy to the mass of an object and to the speed of an object.
- MS-PS3-5 Construct, use, and present arguments to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object.

**Common Core Standards:**

- RST.6-8.3 Follow preciesly a multistep procedure when carrying our experiments, taking measurements, or performing technical tasks.
- WHST.6-8.2 Write informative/explanatory texts, including the narration of historical events, scientific procedures/experiments, or technical processes.
- WHST.6-8.9 Draw evidence from informational texts to support analysis, reflection, and research.

**National Standards:**

- Science as Inquiry Grades 5-8
- Transfer of Energy Grades 5-8
- Motions and Forces Grades 5-8

**Ohio Standards:**

- Grades 6-8 Science as Inquiry Benchmark B
- Grades 6-8 Physical Science Benchmark A

- Potential energy is stored energy due to an objects position or chemical bonds.
- Kinetic energy is the energy of motion.
- When a ball is dropped, the ball's energy is gravitational potential energy (GPE). The force of gravity causes the ball to fall towards the ground. During the fall, the ball's GPE is being converted into kinetic energy (KE). At the moment the ball hits the ground it momentarily stops. The KE has decreased and Elastic Potential Energy has increased to its maximum. Eventually the ball returns to its original shape and bounces back upward. The Elastic Potential Energy changes into KE. As the height of the ball increases, the KE changes into GPE. The rebound height of the ball will never be as tall as the drop height of one meter because some of the energy in this system becomes heat and sound energy. As more of the energy is changed to heat and sound, the ball will eventually come to a stop.

Use of scissors (sharp object) when making the balloon ball.

Students with latex allergies should not handle the balloon ball. These students could conduct the measurements.

Explain expectations and requirements for the use of the balloon ball once they are made.

There are no disposal concerns

Energy conversions between GPE and KE take place in the real world in places such as a swinging pendulum, a teeter-totter, or any dropped object. In sports, the amount of elasticity and rebound of the ball affect the players' abilities and therefore the rules of the game.

Show the students the video clip of a bouncing basketball. Ask the students to draw the basketball at its highest point, when it is falling, when it is at its lowest point, when it is rebounding, and when it is at its highest rebound height. Label the energy conversions taking place in each picture. Identify the pictures with the greatest potential energy and the greatest kinetic energy.

**Grouping Suggestions:** Divide the students into groups of three. The job responsibilities could be the release person, rebound observer and the recorder. All students should help in the creation of the balloon ball.

**Pacing/Suggested Time:** This activity should take approximately 2 class periods.