Jump to main content

Ball Launcher Challenge

1,446 reviews


Try your hand at this engineering challenge. Can you build a "launcher" device to launch a ball as far as possible and a "receiver" to catch it? Building a receiver provides an extra twist to a traditional catapult project. Add to the challenge by using a limited set of materials to build your machine and calculate a score based on your throw distance and materials used.


Areas of Science
Time Required
Short (2-5 days)
Material Availability
Readily available
Very Low (under $20)
No issues
Ben Finio, PhD, Science Buddies

This engineering challenge is based on an internal competition designed by employees at Fluor Corporation.

  • Scotch® is a registered trademark of 3M.
Ball Launcher: 2018 Engineering Challenge


Use craft supplies to build a launching device to throw a ball as far as possible and a receiving device to catch it.


Throwing and catching a ball is something you might easily do with a friend, without giving it much thought. You just "know" how to move your arms, hands, and fingers to throw and catch. Can you imagine building a machine to throw a ball instead? How would it know to throw the ball a certain distance? How could another machine catch the ball without dropping it? This project provides a fun engineering challenge: use common materials to build a "launcher" to throw the ball and a "receiver" to catch it. Figure 1 shows some example devices.

Four images of homemade catapults and receivers

Two catapults are made from pencils, plastic cups, tape and a ruler and are pictured on the left of the image. Two receivers are made from paper, a plastic cup, tape and pencils pictured on the right.

Figure 1. Different designs for launching (left) and receiving devices (right).

This challenge gives you the opportunity to explore some interesting topics in physics and engineering. Rather than explaining each of these topics in detail, this background section will give you a brief overview of each one, and then you can do more research using the links in the bibliography. If you are doing this project for a science fair, do not worry about learning about all of these topics. Choose one or two to learn about in more detail. The bibliography has websites to jump-start your learning.

First, this is a great opportunity to learn about simple machines, like the lever or the inclined plane. You can also investigate more complex machines, like catapults, trebuchets, or slingshots, that are used to launch projectiles. Think about how you could incorporate different aspects of these machines into your design.

You can also use this project to learn about projectile motion. How do the initial velocity (starting speed) and launch angle (angle at which an object leaves the launcher) of a projectile affect its range (distance it travels)? What trajectory (path through the air) will make it easier to catch the ball? A high, steep trajectory or a low, shallow trajectory?

You can also use this project to learn about energy. The ball needs kinetic energy, the energy of motion, in order 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. How could your machine convert one form of energy to another?

Finally, you can use this project to demonstrate the engineering design process. You will probably not think of an idea for a machine, sit down and build it, and have it work perfectly on the first try. You might need to come up with multiple designs, test more than one of them, and modify the designs to improve them. This is OK—real engineers rarely get things right on the first try!

Terms and Concepts



Materials and Equipment

If you are just doing this project for fun or for a school science project, you can use any materials you want. However, if you want to compare your results to those of other students who did the 2018 Engineering Challenge, you can only use the materials listed below. Each item has a maximum allowable quantity and a point cost (each) that will be deducted from your score, as described in the procedure. Note that you can cut the materials, but costs are not pro-rated; e.g. if you cut a piece of paper in half and only use half of it, it still costs 10 points.

Construction Materials
Item Maximum
Point cost (each)
Corrugated cardboard base (max size 12"x12" or 30x30 cm) 1 0
Large paper or plastic cups (16–18 oz, or about 450–500 mL) 4 50
Wooden ruler or paint stirrer (12"/30 cm) 2 100
Paper (printer/copier paper, not construction paper or cardstock; letter or A4 size) 10 10
Wooden pencils (circular or hexagonal cross-section, approx. 7–8" or 18–20 cm length) 10 10
Rubber bands (size 32, 3" long unstretched and 1/8" wide) 10 20
Large paper clips (approx. 2" or 50 mm length) 10 5
Roll of clear adhesive tape (Scotch® tape or equivalent, 1/2" or 3/4" width, max length 500") 1 100

Tools and Testing Materials (no point cost)
Paper and pencilFor sketching design ideas
Scissors For cutting construction materials
Metric tape measure If you only have an inch tape measure, you will need to convert your measurements to centimeters
Sheet of aluminum foil 12"x12" or 30x30 cm sheet, tightly crumpled into a ball with a diameter of no more than 2" (5 cm)
Large, open area of floor space for testing At least 10 feet or 3 meters
Table 1. Allowable materials for the 2018 Engineering Challenge.

Experimental Procedure


Note: the 2018 Engineering Challenge is over, but you can still do this project on your own!

The objective of the 2018 Engineering Challenge was to use limited materials to build one device (the launcher) that launches an aluminum foil ball and another device (the receiver) that catches the ball. The farther your ball flies before being successfully caught by the receiver, the more points you get.


If you want to follow the format of the 2018 Engineering Challenge, you must follow these rules:

  1. You can only use items listed in the table in the materials section to build your launcher and receiver.
    1. The maximum quantities listed are total for the project, not for each separate device.
    2. No other materials are allowed. For example, you cannot build your launcher out of LEGO®.
    3. The cardboard base must remain flat. It cannot be folded, and you cannot cut off smaller pieces to use for construction.
    4. You are allowed to cut the materials (for example, cut a piece of paper in half, cut holes in a cup, etc.). However, point costs for the materials are not pro-rated.
  2. The launcher must fit on top of a 12"x12" (about 30x30 cm) piece of cardboard and cannot extend past the edges of the cardboard. There is no height restriction.
  3. The receiver can measure no more than 12" wide by 12" long (about 30x30 cm). There is no height restriction.
  4. Only one person can operate the launcher at a time.
  5. You can use both hands to load the ball into the launcher. You cannot touch the ball after it is loaded. You cannot use both hands to store energy in the machine (e.g. stretch a rubber band or raise a weight), only to load the ball.
  6. You can use one hand to hold down the cardboard base of the launcher when launching the ball. You cannot hold on to any other part of the launcher in order to stabilize it or prevent it from moving.
  7. You can use only one finger to activate the launcher (if you are holding down the base with one hand, you will use one finger from your other hand). This includes any action that exerts a force or stores energy. For example, pressing on one side of a lever, stretching a rubber band, or lifting a weight into the air can only be done with one finger. You cannot use your whole hand or fist to strike a lever. You cannot use multiple fingers to stretch the rubber band and then include a "trigger" mechanism that allows you to release it with just one finger.
  8. The receiver must be free-standing (it cannot be held in place or stabilized by a person, or taped to the ground). No one is allowed to touch the receiver during a test.
  9. The ball must land and stay in the receiver without touching the ground or anything else (a wall, a person, etc.). The ball cannot roll or bounce into the receiver, or bounce out of the receiver after landing in it initially. If the receiver falls over, but the ball remains in the receiver and does not touch the ground, that is OK.
  10. There is no limit to the number of tests you can do to try to get a higher score, but you can only submit one official score per team.


  1. Make sure you read and understand all the contest rules before you start.
  2. If you are unsure how to start designing, try these tips:
    1. Take some inspiration from other launching or receiving devices you have seen in the real world or online, like slingshots, catapults, a baseball pitcher and glove, bowls, baskets, and nets.
    2. Sketch more than one idea when you are brainstorming.
    3. Compare ideas—remember that the more materials you use, the more points it costs.
    4. If you are working in a team, compare and contrast your ideas and even try combining them to make a better idea.


  1. Once you have decided on a design, build it. If you are working with a team, you may want to assign different jobs to each person in the group to make sure everyone gets a chance to participate. For example: one person can gather the materials, one person can hold the items in place while someone else tapes them together, and one person can monitor the design to make sure it matches the sketch you drew. Or, you could split into sub-teams, and one team can build the launcher while the other team builds the receiver.
  2. You might need to modify your design, even as you build it! For example, you might discover that two parts do not fit together like you thought they would. This is OK and a normal part of the engineering design process. Just be sure to keep track of the materials you use in your final design when you calculate your score (materials you used in earlier prototypes do not count, so do not be afraid to experiment!).


  1. Crumple up a sheet of aluminum foil (12"x12" or 30x30 cm) into a wad with a diameter of less than 2 inches. This will be your "ball."
  2. Experiment with your launcher. Try using it to launch the aluminum foil ball.
    1. Can you operate the launcher as described in the rules (one person uses one hand to hold down the base and one finger to activate the launcher)?
    2. Is the launcher sturdy? Do all the parts stay together? Can it stand up to the stress of repeated launches?
    3. What is the range of your launcher? How far can you launch the ball?
    4. How accurate is the launcher? Can you hit the same spot on the floor more than once?
    5. Are there any changes you can think of to improve the design of the launcher?
  3. Experiment with your receiver. Try using your launcher to launch the ball into it and/or just throwing the ball at the receiver. Remember that you cannot touch the receiver during a test.
    1. How easy is it to hit the receiver? Would changing its size or shape affect this?
    2. How stable is the receiver? Does it fall over when the ball hits it? If so, does the ball stay inside without touching the ground?
    3. How bouncy is the receiver? Does the ball tend to stay in it or bounce out of it?
    4. Can you think of any changes to improve the receiver?
  4. If you are working with teammates, discuss your observations as a group. You might want to modify your launcher and/or receiver design before you start official testing. Remember that this is OK! Real engineers rarely get a design perfect on the first try. You can go back to re-design, re-build, and re-test your design as needed (as time allows).
  5. When you think your design is ready, move on to the next section to try an official test and calculate your score (you will still be allowed to come back and make further changes to your design).

Official Test

When you are ready to do an "official" test and calculate your score, follow these steps:

  1. Place your launcher and receiver on a long, flat surface, like the floor or a countertop.
  2. Use a tape measure to measure the horizontal distance in centimeters between the front of the launcher's base and the closest point on the receiver, as shown in Figure 2. You can make the distance between the launcher and receiver as large as you want—the longer the distance the ball flies before being successfully caught, the better your score will be. A distance of about 30 cm is a reasonable distance to try first.
  3. Launch the ball into the receiver. Remember to follow the rules:
    1. Only one person can operate the launcher. That person can use one hand to hold down the launcher's base and one finger to activate the launcher.
    2. No one can touch the receiver during a test.
    3. The ball must land and stay in the receiver without ever touching the ground.
  4. If you do not get the ball to land in the receiver on your first try, try again (there is no limit on the number of tries). If you are still unsuccessful after a few more attempts, you might need to modify the design of your launcher and/or receiver or reduce the distance between the launcher and receiver (remember, 30 cm is a good distance for a first test). If you are working with a group, discuss the problems you have encountered and make changes to your design and/or test distance if necessary.
  5. If the ball lands in the receiver, move on to the next section to calculate your score. You can always come back to this section to try for a higher score (longer distance).
Diagram measures the distance between a homemade catapult and a receiver
Figure 2. How to measure distance between the launcher and receiver. Measure the horizontal distance from the front of the launcher's base to the closest point on the receiver.


Calculate your score using this equation:

  • The distance in centimeters is the distance between the launcher and the receiver, as shown in Figure 2
  • The materials cost is the sum of the point costs for all the materials used in your final design, as defined in Table 1


For troubleshooting tips, please read our FAQ: Ball Launcher Challenge.

icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.


  • This contest was originally designed with a sports theme modeled after American football, where the launching device is the quarterback. You can try this project with different sports-related twists:
    • Mount a toy basketball hoop on a table or door and try to launch the ball into it from the floor.
    • Launch the ball through two parallel posts, like kicking a field goal in American football.
    • Launch the ball into a net, like scoring a goal in soccer or hockey.
    • Try to launch the ball over a wall from a certain distance away, like hitting a home run in baseball.

Frequently Asked Questions (FAQ)

If you are having trouble with this project, please read the FAQ below. You may find the answer to your question.
Q: Can I use materials not listed in the materials section?
A: If you are doing this project for a science fair or just for fun, you can use whatever materials you want. If you want to compare your scores to high scores from the 2018 Engineering Challenge, you should only use the items listed in the materials section.
Q: Can I use other tools?
A: To keep the competition fair, scissors are the only tools allowed. No power tools, screwdrivers, hobby knives, hot glue guns, etc. may be used for construction.
Q: Do I have to use red plastic cups?
A: No. Paper or other colors of plastic are OK, but the size must be 16–18 oz, or about 450–500 mL.
Q: Am I allowed to cut the materials?
A: Yes, you are allowed to cut the materials (for example, cutting a piece of paper in half or cutting holes in a plastic cup). However, remember that the material costs are not pro-rated. If you cut a piece of paper in half and only use half of it, you must still count the entire piece of paper when calculating your score.
Q: Am I allowed to cut the cardboard base?
A: You can cut the cardboard base if you want to make it smaller, or only have access to smaller pieces of cardboard to begin with. For example, if you can only find a 10"x10" cardboard box, you can use one of the sides as your base. However, the base must remain flat (you cannot fold it up to make walls), and you cannot cut off smaller pieces to use in construction.
Q: I used and then discarded some materials while testing different designs. Do the discarded materials get subtracted from my final score?
A: No, only the materials that are used in your final design are included in your final score. For example, say you build a launcher with three pencils and test it. You then redesign the launcher, remove one of the pencils, and test it again. You would only use two pencils when calculating your final score.
Q: How far apart should my launcher and receiver be?
A: You can set the launcher and receiver as far apart as you want. A good starting distance is about 30 cm. After you master that distance, then you can move them farther apart.
Q: How do I measure the distance between the launcher and receiver? Do I measure from the front or the back?
A: Measure the distance from the front of each device, as shown in Figure 2.
Q: Can I do multiple tries for the official test?
A: Yes. If the ball fails to land in the receiver, you can try again.
Q: Can I keep changing the distance for the official test?
A: Yes. Once you get the ball to land in the receiver without touching the ground, you can move the receiver farther away and try again for a higher score. Report the highest score you achieve.
Q: Can I touch the ball (for example, flicking it) if I just use one finger?
A: No. Once the ball is loaded into the launcher, you cannot touch it directly, even if you just use one finger.
Q: My machine broke during one of my tests. Can I fix it?
A: Yes, but make sure you calculate your score based on the total amount of materials used in the final design. For example, if you completely remove a ripped sheet of paper and replace it with a new sheet of paper, that only counts as one sheet. If you tape a new sheet of paper on top of a ripped sheet of paper, that counts as two sheets.
Q: My receiver fell over when it caught the ball. Does that still count?
A: As long as the ball stayed in the receiver and did not touch the ground, yes.
Q: Does the ball need to be raised up off the ground when it is in the receiver?
A: No. As long as the ball is not touching the ground directly, that is OK. For example, if there is a piece of paper between the ball and the ground, that is OK. If the receiver has walls but no bottom, so the ball sits directly on the ground when it is inside the receiver, that is not OK.


If you like this project, you might enjoy exploring these related careers:

Career Profile
Mechanical engineers are part of your everyday life, designing the spoon you used to eat your breakfast, your breakfast's packaging, the flip-top cap on your toothpaste tube, the zipper on your jacket, the car, bike, or bus you took to school, the chair you sat in, the door handle you grasped and the hinges it opened on, and the ballpoint pen you used to take your test. Virtually every object that you see around you has passed through the hands of a mechanical engineer. Consequently, their… Read more
Career Profile
CAD (computer-aided design) technicians combine art and engineering to prepare the technical drawings and plans from which everything in the world is made—from toys to toasters, houses to hoses, satellites to sewer systems. CAD technicians are essential to the design and construction of everything you see around you. Read more
Career Profile
You use mechanical devices every day—to zip and snap your clothing, open doors, refrigerate and cook your food, get clean water, heat your home, play music, surf the Internet, travel around, and even to brush your teeth. Virtually every object that you see around has been mechanically engineered or designed at some point, requiring the skills of mechanical engineering technicians to create drawings of the product, or to build and test models of the product to find the best design. Read more
Career Profile
Engineering managers not only have to be knowledgeable about engineering, but they also need the right skills to be a good manager. Engineering managers supervise and coordinate a team of engineers. There are many specific engineering fields in which they could work, including manufacturing, electrical design, nuclear engineering, software, aerospace, and many others. Read more

News Feed on This Topic

, ,

Cite This Page

General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Finio, Ben. "Ball Launcher Challenge." Science Buddies, 4 Feb. 2023, https://www.sciencebuddies.org/science-fair-projects/project-ideas/ApMech_p052/mechanical-engineering/build-ball-launcher. Accessed 30 Sep. 2023.

APA Style

Finio, B. (2023, February 4). Ball Launcher Challenge. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/ApMech_p052/mechanical-engineering/build-ball-launcher

Last edit date: 2023-02-04
Free science fair projects.