NOAA uses a pneumatic catapult to launch an unmanned monitoring aircraft.
Photo courtesy of NOAA\Erin Moreland
- Length: Variable
Students explore physical energy and mechanical energy as they design, build and test catapults.
This activity is from the Think Like an Engineer Teacher's Guide. Originally intended for use as an after-school program, the lessons in the unit may be used together to form the basis of a STEM teaching and learning experience for upper elementary and/or middle school students.
What It’s About
Throughout history, warriors and hunters have developed weapons to aid in their battles and pursuit of food. War machines, in particular, have been a focus of technological innovation. As warfare grew more complex, so did weapons. Javelins and boomerangs were tools for both hunting and war. Another device, the atlatl, extended the throwing arm and greatly increased throwing force. Eventually, catapults were invented. Catapults harness physical and/or mechanical energy to launch projectiles. Examples of catapults include slingshots, hurling devices used in castle sieges, and even steam-powered machines that launch airplanes off aircraft carriers.
Catapult technology, first thought to have been developed in Greece as early as 50 BCE, was initially used to increase the range and penetration of arrows. When released, a catapult would shoot a large arrow toward the enemy.
Later, more powerful catapults were able to launch large stones, biological weapons (e.g., a hornets’ nest), incendiary bombs, and even terror projectiles like the heads of the captured! The history of catapults includes a large variety of designs, each with a different purpose.
Objectives and Standards
Students must answer the following question.
Can you design and construct a catapult that meets specific goals, such as being most accurate, firing the greatest distance, or launching the heaviest projectile?
Materials and Setup
Bag of marshmallows or gummy bears (to use as projectiles)
Foam building blocks
Materials per Student Group
2 survey flags or plastic orange cones
Bulls-eye target, or paper to create a target
Manual tennis ball thrower with tennis ball (available at pet stores)
Tape measures or metersticks
Materials per Student
At least 20 craft sticks, notched craft sticks, chopsticks, or wooden skewers with sharp ends removed
Copy of “Catapults,” and “Build a Spoonapult” pages
Prepare bags of materials for each team of students.
Procedure and Extensions
Time: 1–2 Sessions
What To Do: Launching Projectiles
Ask students, How far do you think you can throw a tennis ball? Take them outside and give all students a chance to throw the ball as far as they can. Use masking tape to indicate the distance achieved by each student.
Next, ask Is there any way you could throw the ball further? Introduce the atlatl, a stick that extends from the arm of the thrower. The atlatl has been used by ancient Egyptians, Inuits of the Arctic Circle, and Aztecs of Mexico, among others.
A spear would be affixed to the end of the atlatl, which provided extra arm length that enabled the thrower to produce greater acceleration of the spear than would be possible without this tool. Modern day ball throwers for dog owners employ the same principle.
Have students use a ball thrower to throw the tennis ball again. Mark the new distances and compare them to the original measurements.
Return to the classroom and lead a discussion of students’ observations. Ask, How far could you throw the tennis ball using just your arm? How far did you throw it with atlatl? Do you think there is a limit to how long an atlatl can be and still work? Is there a limit to how heavy a projectile can be thrown with an atlatl?
What To Do: Spoonapults
Review students’ experiences with the atlatl and remind them of their answers to the questions above. Tell them that a catapult can launch a boulder hundreds of meters. In fact, the Greeks were engineering war machines as early as 400 BCE. They had perfected the bow and arrow, but for mass warfare, they sought more powerful weapons. Initially, the catapult was designed to launch several arrows at once, but over time, it was refined into a mighty machine that also could hurl large rocks, biological weapons and even the heads of enemies.
Show pictures of catapults (see PDF) and discuss key design characteristics. Have students use craft sticks to build an equilateral triangle and square base, and then test the stability of each design. Be sure they understand that a catapult requires a stable base to launch projectiles.
Explain that students will investigate catapults by building and testing a “spoonapult,” which uses a plastic spoon to launch projectiles. Have each student team construct a spoonapult, following the illustrations on the student sheet. Then, direct teams to test their spoonapults by launching marshmallows toward a bullseye placed on the floor.
Discuss the results of students’ first spoonapult construction challenge. Ask, How well did your spoonapult work? How far did it fling the marshmallows? Was your spoonapult accurate?
Have student teams follow the engineering model to build a better spoonapult. Remind teams that their development process should include sharing ideas (brainstorming solutions), designing a plan, building the new spoonapult, and then testing, evaluating and refining their designs.
Build a small castle out of foam blocks. Challenge teams to “destroy” the castle with their newly created spoonapults by launching projectiles from a distance of three meters.
Have students bring in materials to make a larger catapult, capable of launching a tennis ball or small water-filled balloon at least 10 meters.
Funded by the following grant(s)
Grant Number: DRL-1028771