# Balloon Ball Bounce

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Goal: Students will explore potential and kinetic energy in the construction of a â€śsuper ballâ€ť made of round balloons.Â  Understanding this idea, the students will determine if the number of balloons in a balloon ball affect the rebound height.

Objective: TLW investigate the energy conversions and the rebound of a student-made balloon ball. Through the activity, the students might also identify variables, collect data, and create an accurate graph of data and draw conclusions from the data.

Materials: Consider gathering the following materials for each student group: 10-12 round balloons, a meter stick, and scissors.Â  Students will also need science journals or other paper to record data.

Teacher Background Knowledge: Potential energy is stored energy due to an objects position or chemical bonds.Â  Kinetic energy is the energy of motion.Â  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 comes to a stop.

How to Make a Balloon Ball: To make the balloon ball:

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

See video demonstration: http://agpa.uakron.edu/p16/video.php?id=balloonball&lp=balloonball&pg=procedures

Engagement: Ask 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.) See: http://www.exploratorium.edu/baseball/bouncing_balls.html

Exploration: Challenge students to use the balloons to make a balloon ball. They are to design a ball for a sport that needs the greatest possible rebound when dropped from a height of 1.0 meter. Divide the students into groups of three (this will allow for 3 jobs: release person, distance observer and a recorder). All students should assist in the creation of the balloon ball. For older students: decide how many balloons they will use in their balloon ball. However, they will need to test at least three different balls.

In this, 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.

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).Â  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.

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

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. 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? For older students: 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.

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