Before You Start
Get everything you need
🧰 Materials
7 craft sticks (popsicle sticks)
4–5 rubber bands (various thicknesses)
1 plastic spoon
Mini marshmallows (20+)
Tape (optional)
Catapult Blueprint printable
Target Practice Score Sheet printable
Ruler or tape measure
⚠️ Safety First!
Never aim the catapult at a person's face — always launch toward a clear, safe target!
Never aim the catapult at a person's face or eyes
Always launch toward a clear, safe target area
Adult assistance required for children under 6 with rubber bands
Check rubber bands for cracks before use
What You'll Do
🍡
You're going to build a real working catapult out of craft sticks and rubber bands — just like a tiny, safe version of a medieval siege weapon — and use it to launch marshmallows at targets!
When you pull back the spoon, you're stretching the rubber band and storing up energy inside it, called elastic potential energy. The moment you let go, all that stored energy turns into motion energy and launches your marshmallow flying through the air!
After your first launches, you'll test something important: does pulling back farther really make the marshmallow fly farther? You'll measure and find out for yourself.
Marshmallow Catapult Build Challenge
Follow along carefully
Build the Base
🪵
Stack 5 craft sticks together in a neat pile. Wrap a rubber band tightly around each end — this is your base.
Tip: Wrap each rubber band 3–4 times for a really tight hold!
2
Make the Arm
🦾
Take 2 more craft sticks. Wrap ONE rubber band around ONE end of both sticks together — leave the other end free.
Tip: This becomes the launching arm of your catapult!
3
Assemble the Cross
➕
Slide the stack of 5 sticks between the 2 sticks at the FREE (open) end. They form a cross or + shape.
Tip: Make sure the cross sits right in the middle for balance!
4
Add the Engine
🔗
Wrap a rubber band in a big X pattern right at the cross point. Pull it tight — this is the engine.
Tip: The tighter this X, the more powerful your launches will be!
5
Attach the Spoon
🥄
Attach a plastic spoon to the TOP single stick using rubber band or tape. Make sure the bowl faces UP.
Tip: Double check the spoon bowl faces up before testing!
6
Launch and Measure
🚀
Place a mini marshmallow in the spoon. Pull the spoon back and release! Mark where it lands and measure the distance.
Tip: Test small, medium, and maximum pull-back distances and compare!
Try It Different Ways
🎨
Little Kids (5-6)
An adult helps wrap the rubber bands tightly, especially the X-pattern engine. Little ones can place marshmallows and pull the spoon back to launch.
🔬
Big Kids (7-8)
Build the entire catapult independently and test 3 different pull-back distances, recording results on the Score Sheet.
🧪
Challenge!
Try to hit a paper cup target from 3 feet away. Adjust your aim by tilting the base — how accurate can you get after several tries?
What's Happening?
🧒 Kid Explanation
When you pull the spoon back, you're stretching the rubber bands — and stretchy things like to store up energy while they're being pulled. The more you pull, the more energy gets packed in, just waiting to be let loose!
The instant you let go, all that stored-up energy turns into movement, and SNAP — your marshmallow goes flying! Pulling back farther stores more energy, which is exactly why a bigger pull-back sends the marshmallow farther through the air.
🔬 Grown-Up Explanation
This activity demonstrates the conversion of elastic potential energy into kinetic energy. Stretching the rubber band stores mechanical energy proportional to the distance it is displaced from its resting position. Upon release, this stored energy converts almost entirely into kinetic energy, propelling the marshmallow along a parabolic trajectory determined by the launch angle and initial velocity. Greater pull-back distance increases the stored elastic potential energy, resulting in a higher launch velocity and greater range.
This directly supports NGSS K-PS2-1 (investigating the effect of different strengths of pushes) and K-2-ETS1-3 (analyzing data from tests of two objects designed to solve the same problem).