Ball Launcher Challenge

Background Information for Teachers

This section contains a quick review for teachers of the science and concepts covered in this lesson.

In this lesson, your students will use readily available craft/office supplies to build a device that can launch a ball and a receiver to catch it (Figure 1). Detailed rules and scoring guidelines are provided so you can hold a class-wide competition and compare your class's scores to those submitted by other students around the world during the 2018 Engineering Challenge.

This challenge gives you the opportunity to explore some interesting topics in physics and engineering. Rather than explaining each topic in detail, this background section will give you a brief overview of each one, and you can decide which, if any, to address with your students. Explanations of each topic can be found in the Additional Background Links section.

• Simple machines: use the project to learn about simple machines like the lever and inclined plane. How can simple machines be combined to form a more complex machine that can launch a ball?
• Projectile motion is a classic topic in physics classes. How do the initial and launch angle of the ball affect its range?
• Energy is another classic physics topic. The ball needs kinetic energy, the energy of motion, to fly through the air. Where will that energy come from? It could come from elastic potential energy, the energy stored in a stretched material, like a rubber band. It could come from gravitational potential energy, the energy stored in an object that is raised up off the ground. Or, the energy could come from work that you do with your hand by exerting a force.
• Engineering design: you can also use this project to walk your students through the engineering design process. They probably will not build a perfect machine on their first try. Instead, they will need to iteratively test and redesign their launcher/receiver in order to improve the design.

Additional Background Links

• Simple Machines, Science Trek
• The Physics of Catapult Projectile Motion, Science Buddies
• What is a Projectile?, The Physics Classroom
• Engineering Design Process, Science Buddies

Prep Work (15 minutes)

• Take a few minutes to review the instructions document and the introductory video for the challenge.
• You may need to rearrange furniture in your classroom to clear a testing area for the ball launchers. Successful launchers can throw a ball pretty far, so you should be prepared to let your students test in the hallway or gymnasium/cafeteria etc.

Engage (5 minutes)

Introduce the challenge to your students. Explain that their main goal is to build a device that can launch a ball as far as possible, and a receiver to catch the ball without letting it touch the ground. However, there are rules they have to follow and they are only allowed to use certain materials. You can show the introductory video to your students and/or go over the instructions document with them.

Explore (90 minutes)

1. Design: before they start building, encourage your students to sketch potential designs for both launching and receiving devices. Each group member can start by sketching their own ideas, then they can compare. They have a range of different materials available to them. What materials will they use for what purpose? Different group members probably have different ideas. How well does each idea follow all the rules for the competition? What about the limitations on materials? Can they evaluate all their proposed ideas and agree on which one they should build? What about combining aspects of different ideas into one new design?
2. Build: once the group has agreed on a design, they should build a prototype. The might discover right away that things do not always go as planned. Maybe the pieces of their design do not fit together as well as they planned, or the materials are not strong enough to do what they expected. Remind students that this is OK! They are allowed to modify their design to improve it when they discover problems.
3. Test: when students are ready to test their prototype, they should bring their launcher and receiver to an open area for testing. Try launching the ball into the receiver (make sure they follow the rules for operating the launcher and receiver, outlined in the instructions document), and make observations. What happens when they launch the ball? How far does it go? How accurately can they aim the ball towards the receiver? Do their devices hold up to repeated launching/receiving or start to fall apart? Depending on what they observe, they will need to decide how to modify or improve their design.
4. Iterate: engineers rarely get something perfect on the first try! Now that they have tested their design once, it is time to improve it and retest. Look at the scoring document. There are two ways you can improve your score: launching the ball farther, and using fewer materials. But it only counts as a successful launch if the ball lands in the receiver without ever touching the ground. So to improve your score, you need to build a launcher that can launch the ball far and accurately—no points for distance if you miss the receiver! Can you remove some materials from either the launcher or receiver while maintaining their functionality? Keep iterating until you are convinced you have the best possible device, given all the constraints.

Reflect (30 minutes)

Once students have finished building their devices, have a class-wide competition to calculate their official scores.

1. Inspect each device to make sure it follows the rules (e.g. fits within the required dimensions, does not use more than the allowed quantity for each material).
2. Inform the students how many tries or how much time they will get to go for a high score (e.g. "10 tries" or "as many launches as you can make in two minutes").
3. Let the students choose how far apart to place their launcher and receiver for their first try. Use a tape measure to measure the distance between the launcher and the receiver, and write this distance down.
4. Let the students start launching the ball (remember to follow the rules about how to operate the launcher).
5. As soon as they have a successful launch/reception (ball never touches the ground), they can move the receiver farther away and keep trying for a higher score.
6. Repeat this process until they run out of tries or time.
7. Move on to the next group.

Use the scoring spreadsheet or worksheet to calculate the final score for each group.

Discuss the results of the competition as a class.

• How similar/different were the designs people drew initially?
• How similar/different were the designs people decided to build?
• What problems did groups encounter during the building/testing process?
• Do the most successful designs have anything in common?

Assess

• Collect your students' worksheets and use them to assess how they worked through the design process.
• Ask each group to do an oral presentation about how their design worked, the engineering challenges they faced, and how they addressed them.

Lesson Plan Variations

• Did your students enjoy this type of hands-on project? Check out the other Engineering Challenges and try them in your classroom!