Build a Popsicle-Stick Catapult
A hands-on look at levers, tension, and iterative design — build one, test it, then improve it.
Related field: Mechanical Engineering
Mission Briefing
Objective
Build a small catapult that can launch a light object as far and as consistently as possible.
Constraints
- Must be built only from the materials listed below — no additional store-bought launch mechanisms
- The launched item must be something soft and safe, like a pom-pom or mini marshmallow
- Take 3–5 test launches before you're allowed to change the design
Concept You're Testing
Levers and stored energy — how arm length, pivot position, and rubber-band tension change how much force gets transferred to the launched object.
What You'll Need
- About 10 popsicle sticks (craft sticks)
- 6–8 rubber bands
- 1 plastic spoon
- A small item to launch, like a pom-pom or a mini marshmallow
- Hot glue gun or strong tape
Ask an adult before using a hot glue gun, and always aim the launch away from faces and breakable objects.
Instructions
- 1Stack 5 popsicle sticks together and wrap a rubber band tightly around each end — this is your base.
- 2Take 2 more sticks and rubber-band them together tightly at just one end, so they can still pivot open like scissors — this becomes the spacer arm.
- 3Slide the base between the two sticks of the spacer arm, as close to the rubber-banded end as possible, and secure it with another rubber band in an X pattern to lock it in place.
- 4Glue or tape the plastic spoon to the top of the loose end of the spacer arm — this is your launch arm.
- 5Place a small item in the spoon, hold the base down, pull the spoon back, and let go.
- 6Test 3–5 launches and note roughly how far the item travels each time.
- 7Change one thing — number of rubber bands, spoon angle, or number of base sticks — and test again. Compare the results.
How to Measure Results
Measure the distance of at least 3 launches with a tape measure or by counting floor tiles, then compare the average distance before and after you change one variable.
Skills You'll Practice
- Basic lever and torque mechanics — why arm length and pivot position change launch force
- How stored energy (rubber band tension) converts into motion
- Iterative design — changing one variable at a time and measuring the effect
- Comfort with a design not working perfectly on the first try
If It Doesn't Work the First Time
That's normal — this challenge follows the same design process real engineers use. A failed test just tells you where to go back and improve.
Figure out what problem you're actually solving, and what would even count as success. Skip this step and jump straight to building, and a lot of bad designs happen right here.