Ping Pong Pickup Challenge for Grades 9-12

Background Information for Teachers

You can use devices like the one in Figure 1 to pick up trash, reach things on shelves, or even just grab something from a chair if you are too lazy to get up! They can also save you from touching dirty things with your hands. The devices need to be sturdy enough to reach for things that are far away without bending or breaking, but also light enough that they are easy for people to use. They also need to maintain a firm grip on whatever you are picking up so you do not drop it.

Image Credit: Pydio / purchased watermark-free version
Figure 1. A trash grabber picking up a plastic bottle.

The 2023 Engineering Challenge is inspired by devices like the one in Figure 1. The goal is to build a device using nothing but paper, tape, string, and paper clips that can pick up and retrieve a ping pong ball from a distance. The farther away the ball is, and the fewer materials you use to build your device, the higher the score will be.

You can use this challenge to explore several different topics in physics and engineering with your students. How you approach the project is up to you. First, it is a good way to practice the engineering design process. You can also explore simple machines and various mechanisms with your students. They can apply knowledge about material properties like mass, stiffness, and friction, and use that knowledge to make informed decisions about how they build their devices.

Additional Background Links

• The Engineering Design Process, Science Buddies.

Prep Work (15 minutes)

• Gather all the construction materials in a central location for students.
• Print the Student Worksheets (one for each student)
• Optional: assign the Introductory Video for your students to watch before class.
• Set up testing areas for students. For each testing area, put a small square of tape on the floor and place a ping pong ball inside the square. Then, mark distances in increments from the square (10 cm, 20 cm, 30 cm, etc.) to make it easier for students to test at increasing distances.

Engage (15 minutes)

Introduce the challenge to your students. Explain that their main goal is to build a device that can pick up and retrieve a ping pong ball from as far away as possible. Show your students the introductory video if they have not watched it already. Then, go over the student worksheet and the contest rules (also included in the student worksheet):

Rules

1. The ball and the start line must both be on the floor.
2. The ball must start a minimum of 10 cm from the start line (Figure 3). After that, you can increase the distance for subsequent trials.
3. The ball must be placed directly on the floor. You can place a small square of tape around the ball to prevent it from rolling away and make it easier to know where to place the ball during trials.
4. The ball cannot be modified in any way.
5. The device must be portable. It cannot be taped or otherwise anchored to the ground or another surface like a piece of furniture.
6. Only one person can operate the device during a trial. It does not have to be the same team member for each trial.
7. No part of your body can cross the start line at any point.
8. The ball cannot touch any surfaces or objects other than the floor and your device.
9. After the ball has been picked up, no part of the device or the ball can touch the ground or any other surface (walls, furniture, etc.) in front of the start line. The device and/or ball may touch the ground behind the start line.
10. The ball must remain in contact with your device and cannot become airborne at any point while it is still in front of the start line.
11. You cannot touch the ball directly at any point once the trial has started, even after you have brought it back behind the start line.
12. For a successful trial, the ball must be picked up, brought back behind the start line, and placed on the floor.
13. Nothing can remain stuck or attached to the ball after it has been deposited behind the start line.

Image Credit: Ben Finio, Science Buddies / Science Buddies

A side-view diagram of a person standing on the floor and holding a grabbing device, reaching for a ping pong ball that is at least 10cm away. No part of the person's body can cross the start line on the floor. The distance is measured from the start line to the closest side of the ping pong ball.

Figure 3. A side-view diagram of the setup for the ping pong pickup challenge.

Explore (1-2 hours)

1. Background research. Students should do background research about different types of pickup tools, their features, and the materials used to make them. Note that similar devices might be called by different names, such as a grabber, picker, or scooper.
2. Design. Before they start building anything, have each student draw two ideas for a pickup tool on their worksheet. Remind them to think about the materials they are allowed to use, and how they can use those materials to build. For example, a single flat sheet of paper is very flexible, but you can make very stiff structures by folding or rolling paper. They should also think about how the final score will be calculated. It depends on both the distance to the ball and the amount of materials they use.
3. Compare. After drawing two designs, have each student work independently to compare their first and second design, and think about which design would work better for the challenge.
4. Share. Have students form groups and share their designs with other students in their group. Students should compare the designs and discuss which one(s) would score best for the contest. Make sure students evaluate the designs objectively using specific criteria (e.g. the material points cost for each design and its length), as opposed to subjective criteria like appearance. Students can also consider other criteria that are not directly included in the score calculation, such as reliability and ease of construction. Each group should select a single design to build. Designs can include a combination of ideas from multiple students.
5. Build. After agreeing on a single design to build, students should start building it. One device per group. They may need to make changes or adjustments as they build. This is OK.
6. Test. Students should develop an agreed-upon plan before they start testing. How will they evaluate if a design is "working" or meeting the design criteria? Will they test their device at shorter distances before trying for longer distances? Will they conduct multiple trials at each distance? Students should make and record observations while they test their devices.
7. Evaluate. Based on their testing and observations, students should evaluate their design in the context of the design criteria and trade-offs. Is their device working as intended? Can they think of ways to improve its performance, reliability, ease of use, or score?
8. Iterate. Based on their observations, students should try to improve their design so they can increase their score. This can include making the device longer to grab the ball from farther away, but also efficient use of materials to decrease the material points cost.
9. Re-test. After making improvements, students should re-test their devices. Emphasize that it is OK if the tool does not work on the first try (or second, or third...)! This is why engineers test things, so they can fix them and make improvements. Allow your students to continue improving and re-testing their devices as time allows.

Reflect (20 minutes)

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

1. Make sure each group has counted the total quantity of each material used in their final design. Materials used in earlier prototypes do not count. Record these quantities in the student worksheet.
2. If you have not already, put a small square of tape on the floor and place a ping pong ball inside the square. Then, mark distances in increments from the square (10 cm, 20 cm, 30 cm, etc.) to make it easier for students to test at increasing distances.
3. One at a time, let one member from each group stand behind the closest start line with their device, and try to retrieve the ping pong ball. Watch carefully and make sure they follow all the rules (not crossing the start line with their body, etc.). If they break a rule, they must start over.
4. Let groups that succeeded at the closest start line try again from the next-farthest start line. Continue this process until all groups have maxed out their distance and can no longer retrieve the ball.
5. Each group should record the longest distance at which they could successfully retrieve the ball, and then calculate their score using the student worksheet. An example calculation is provided below for your reference.

First, tally up the total quantity for each material used in your device. Remember that materials used in previous iterations do not count, only materials used in the device that you used for the official test.

Next, add up your material points cost using these values:

1. Paper: 5 points per sheet (rounded up to the nearest whole sheet)
2. Paper clips: 1 point each
3. String: 1 point per 50 cm (rounded up to the nearest 50 cm)
4. Tape: free

Finally, calculate your score using this equation:

For example, a device that uses two pieces of paper, two paper clips, tape, and no string would have a material points cost of:

If the device picked up the ball from a distance of 30 cm, the score would be:

Discuss the results of the competition as a class.

• Did any students have similar initial designs? Did anyone draw a design that nobody else thought of?
• What about the final design each group picked? Are any designs similar? Different?
• What engineering tradeoffs did groups make in their designs?
• What challenges did groups encounter and how did they address them?

Assess

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

Make Career Connections

Discussing or reading about these careers can help students make important connections between the in-class lesson and STEM job opportunities in the real world.

Mechanical Engineer

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Career Profile

Did you enjoy designing, building, and testing your own device? Thinking about the properties of different materials and how you could use them to build? Mechanical engineers design and build many of the devices we use every day. Read more

Engineering Manager

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Career Profile

Engineers frequently work on complex systems that are too much for just one person to design and build. Engineering managers help coordinate whole teams of engineers to make sure everyone is working well together. Did you enjoy working on a team? Did you help assign different tasks to different people? You may have been acting like a manager! Read more

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!