Rosie Labs: Pom Pom Propulsion

Time: 40 to 50 minutes (build plus launch testing)

Big idea: The size and direction of a force determine how an object moves. Students build a launcher, store force in a stretched balloon, and measure how far their pom poms fly.

Standards Snapshot: Virginia SOL + NGSS

Pick your grade band. The build is the same, the thinking changes.

Grade	Virginia SOL	NGSS	Students walk away able to…
K	K.2: pushes and pulls affect the motion of objects	K-PS2-1 · K-PS2-2	Show that a bigger pull makes a bigger flight, and aim the launcher to change where the pom pom goes.
1	1.2: forces change the speed and direction an object moves	—	Describe how their pull changed the pom pom’s speed and direction.
3	3.2: the direction and size of force affects the motion of an object (primary fit)	3-PS2-1 · 3-PS2-2	Test how stretch distance changes flight distance, measure it, and use the pattern to predict the next launch.
5	5.2: forces and energy affect the motion of objects	—	Explain that the stretched balloon stores energy that transforms into motion at release, and run a fair test with variables and constants.
Looking ahead	Middle school physical science	MS-PS2-1 (Newton’s laws)	Newton’s action-reaction idea, introduced here as a story, becomes the assessed standard in middle school.
K–5	X.1: Scientific and Engineering Practices	K-2/3-5-ETS1-2, ETS1-3	Predict, launch, measure, compare designs, and improve based on evidence.

Practices exercised (both frameworks): asking questions and predicting · planning and carrying out investigations (identifying variables and constants at grade 5) · measuring and charting data · constructing explanations from evidence. NGSS Crosscutting Concept: Cause and Effect · Energy and Matter (grade 5).

Curiosity & Wonder

Hold up one pom pom.

“I want this pom pom to reach the back wall. But here is my problem: I am not allowed to throw it, and once it launches, nothing can be touching it. So the push has to be stored up ahead of time and released all at once. What could we build that stores a push?”

Take ideas. Slingshots, springs, and rubber bands will come up, and every one of those answers is correct physics. “Today we build a machine that stores your pull and turns it into flight. Then we find out exactly what makes it fly farther.”

The Build

Materials per student: balloon, craft paper roll, rubber band, scissors, mini pom poms.

1. Tie a knot in the open end of an un-inflated balloon.
2. Cut the balloon in half at the center. Keep the half with the knot; recycle the other half.
3. Stretch the open, cut end of the balloon over one end of the craft paper roll.
4. Wrap a rubber band around the balloon on the roll to lock it in place.
5. Drop in one pom pom (start with one; more come later, and that is the experiment).
6. Hold the roll in one hand, pull back the knotted end with the other. Stretch it, but not so far it pops off.
7. Release. Flight!

Productive struggle moments

Our STEM projects are designed so that participants get it wrong before they get it right. You will observe your students struggling as they attempt to create their own STEM projects. This process is an empowering experience, building perseverance, frustration tolerance and growing overall confidence! With your support, students will step out of their comfort zones to think, build and problem-solve for themselves.

• Tying a knot in an un-inflated balloon is slippery, floppy work. Three tries is the point.
• Cutting the balloon cleanly takes scissor control on a wobbly material.
• The rubber band attachment is the make-or-break step. A loose band means the balloon pops off mid-launch. Ask: “Did your balloon come off? What does that tell you about your rubber band?”
• The weak launch is a diagnosis waiting to happen. Pom poms that flop out the end mean a small stretch, a leaky seal, or a slipped balloon. Compare a strong launcher to a weak one and hunt the difference.

When frustration shows up, narrate instead of fixing: “You are doing the hard part right now. What is one thing you could try differently?” And set the safety rule before the first launch: launchers aim at open floor or targets, never at people, and only pom poms go in the tube.

The Investigation

The launcher is a force machine with two dials, and standard 3.2 is literally about both: the size and the direction of a force.

Dial 1, force size: the Stretch Test. Mark a launch line with tape. Launch with a small pull, a medium pull, and a big pull, and mark where the pom pom lands each time. Predict first: “If I double my stretch, what happens to the distance?”

• K to 1: compare “little pull” and “big pull” landings. Bigger pull, bigger flight.
• Grade 3: measure each distance with a tape measure and chart it. Then use the pattern to predict: “Where will a medium pull land?” Test the prediction. That is 3-PS2-2 in one move.
• Grade 5: run it as a fair test. Independent variable: stretch distance. Dependent variable: flight distance. Constants: same pom pom, same launcher, same angle. Three trials per stretch, then average. Identifying variables and constants is the grade 5 practice standard, word for word.

Dial 2, force direction: aim. Launch flat, launch angled up, launch angled down. Where does each land? Direction of force changes direction of motion, and now they have proven it.

Dial 3, the load: your original step 7. One pom pom versus five versus a full tube. Predict, then test. (The same stored force gets shared across more passengers, so crowded pom poms fly shorter.) Ask grade 5 to explain WHY in energy terms.

Explain the mechanism (grade-band it):

• K to 1: Your pull gets stored in the stretchy balloon. When you let go, the balloon gives the pom pom a big push.
• Grade 3: The applied force comes from the balloon pushing the pom pom. A bigger stretch stores a bigger force, and a bigger force means faster, farther motion.
• Grade 5: The stretched balloon stores energy. At release, that stored energy transforms into motion energy in the pom pom. More stretch means more stored energy; more pom poms means the energy is shared, so each one gets less.

The Newton story (grades 3+): Isaac Newton noticed in the 1600s that every push comes with a push back: for every action, an equal and opposite reaction. Students can feel it: the balloon pushes the pom pom forward, and the launcher nudges back against their hand. Rockets fly on this exact idea, throwing exhaust one way to be pushed the other. The full law is a middle school standard; today it is just a great story with evidence in their hands.

Skills in Practice

• “I predict a bigger stretch will ___ because ___.”
• “My pom pom flew ___ with a small pull and ___ with a big pull.”
• “My evidence shows the size of the force changes ___.”
• “To make it a fair test, I kept ___ the same and only changed ___.”

Real-World Connection

Stored-force launchers are everywhere: slingshots, bows and arrows, pinball plungers, crossbows, and the spring in a retractable pen. And real propulsion systems, from propellers to jet engines to rockets, are all machines built to answer today’s exact question: how do we make a bigger force in the right direction? Ask: “What is something at home that stores a push or a pull until you release it?”

Evidence of Learning

• K to 1: Student demonstrates a small pull and a big pull and says which made the pom pom fly farther.
• Grade 3: Student states one sentence connecting force size to distance, backed by two of their measurements.
• Grade 5: Student writes 2 to 3 sentences explaining a launch using the words stored energy and force, and names their variable and one constant from the fair test.

Vocabulary

• force: a push or a pull.
• applied force: a force one object puts on another, like the balloon pushing the pom pom.
• propulsion: pushing or driving an object forward.
• stored energy (grades 3+): energy held in a stretched or squeezed object, waiting to be released.