With Tek
How to make a balloon car that zooms
To make a balloon car, tape two straws across a small plastic bottle, slide skewer axles through them with a cardboard wheel on each end, then tape a balloon on a bendy straw on top, pointing out the back. Blow it up, let go, and the air rushing back pushes the car forward. In this course your kid learns why a balloon zooms, builds a bottle racer, fixes friction and crooked axles to make it faster, and holds a fair race on the floor. Tek hosts four short films for kids 6 to 13, with a grown-up helping with the cutting and the balloon. Plan about 4 minutes of films and about an hour of building and racing. On Kubrio, all four films and the quiz are free, with no account, and your kid ends with a balloon-powered racer and a race result marked on the floor.
All 4 lessons and the quiz are free on this page. Your kid doesn't need an account. See every lesson
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▶ 1:45 tourWhat your kid makes
Your kid ends with a working balloon-powered racer made from a bottle, straws, skewers, and cardboard wheels, and a race result marked on the floor with sticky notes. Along the way they learn the push-back idea behind every rocket and the friction that slows every car.
- Ages
- 6 to 13
- Time
- 4 films, about 4 minutes, then about an hour of building and racing
- You need
- A small plastic bottle, three straws, one of them bendy, two wooden skewers, with the sharp tips snipped off by a grown-up, cardboard and a cup to trace, tape and a balloon, a grown-up to help with cutting and the balloon, sticky notes for the race
- Host
- Tek
The 4 lessons
Lesson 1. Air goes back
When you push something away, it pushes you back. The balloon pushes air out the back, and the air pushes the balloon forward.
- Blow up a balloon and pinch the end
- Let it go and watch it zip around
- Notice the air going one way and the balloon the other
Where: At home
Lesson 2. Build your racer
A bottle on its side becomes the body, skewers spinning inside straws become the axles, and a balloon taped to a bendy straw becomes the engine.
- Trace four cup-sized wheels, and a grown-up cuts them and pokes the holes
- Tape two straws across the bottle and slide the axles through
- Tape the balloon engine on top, with the straw pointing out the back
Where: At home
Lesson 3. Make it faster
Rubbing that slows things down is called friction. Free-spinning wheels, straight axles, a straw pointing straight back, and a light car all go farther.
- Flick each wheel and slide it out a little if it rubs
- Line the axles up straight, side by side
- Point the straw straight back and test drive again
Where: At home
Lesson 4. Race day
A fair race keeps the start line and the number of breaths the same. More air pushes for longer, and rugs make more friction than smooth floors.
- Tape a start line on a long, smooth floor
- Blow up every balloon with the same number of breaths
- Mark where each car stops, then try a rug
Where: At home
Take the quiz
Tek asks 3 questions about the films. Get 2 right and you finish the course.
Transcript
Lesson 1: Air goes back
Hi, I'm Tek! Today you build a racer with no motor and no batteries. A balloon makes it zoom!
Blow up a balloon, and let it go. Whoosh! It zips around the room. But why?
The stretchy balloon squeezes the air inside. The air rushes out of the little hole, fast.
Here's the big idea. When you push something away, it pushes you back. Push off the wall in a pool, and you glide the other way.
The balloon pushes air out the back. The air pushes the balloon forward. Air goes back, balloon goes forward!
Now put that balloon on wheels, and point the hole backward. All that push moves your car forward.
Your turn. Blow up a balloon, pinch the end, and let it go. Watch the air go one way, and the balloon go the other!
Lesson 2: Build your racer
Let's build! You need a small bottle, three straws, one bendy, two skewers, cardboard, tape, and a balloon.
First, the wheels. Trace a cup on cardboard, four times. A grown-up helps cut them out, and pokes a hole in each.
Lay the bottle on its side. Tape the two straws across the bottom, one near the front and one near the back.
Slide a skewer through each straw. That's an axle, and it spins inside the straw. Tape a wheel onto each end.
Now the engine. Slide the bendy straw into the balloon, and wrap tape around it tight. No air should leak out.
Tape the engine on top of the bottle, with the straw pointing out the back. Your racer is ready!
Your turn. Make four wheels, add the axles, and tape on your balloon engine.
Lesson 3: Make it faster
Time for a test drive! Blow up the balloon through the straw, pinch it, set the car down, and let go.
Slow, or stuck? Something is rubbing. Rubbing that slows things down is called friction.
Give each wheel a flick. It should spin and spin. If it rubs the bottle or the straw, slide it out a little.
Look underneath. The two axles should go straight across, side by side. Crooked axles make your car curve.
Point the straw straight back, too. If it points to one side, the push turns your car.
And keep it light! The same push moves a light car faster than a heavy one.
Your turn. Flick every wheel, straighten the axles and the straw, and test drive it again.
Lesson 4: Race day
It's race day! Find a long, smooth floor, like a hallway or the kitchen.
Put a strip of tape on the floor. That's the start line. Every car starts right behind it.
Make it a fair race. Everyone blows up their balloon with the same number of breaths. Three, two, one, go!
Put a sticky note where each car stops. The car that goes the farthest wins.
Want to go farther? More air pushes for longer. Try four breaths instead of three!
Now try a rug. The cars stop sooner. Soft, bumpy floors make more friction.
Your turn. Race your car on the floor, and mark where it stops. You made a balloon-powered racer!
Free guides to practise with
Questions parents ask
How does a balloon car work?
The stretchy balloon squeezes the air out through the straw, fast. When something pushes air backward, the air pushes it forward, the same way you glide away when you push off a pool wall. So the air goes out the back and the car rolls forward.
Is a balloon car safe for young kids?
Balloons are a choking hazard for kids under 8. Uninflated balloons and broken pieces can block a child's airway, so a grown-up stays close, keeps spare balloons put away, and throws away any popped pieces right away. Before building, a grown-up snips the sharp tips off the skewers, cuts out the cardboard wheels, and pokes the holes.
Why won't my kid's balloon car move?
Something is usually rubbing. Flick each wheel: it should spin and spin, and if it rubs the bottle or the straw, slide it out a little. Check that both axles go straight across, that the straw points straight back, and that no air leaks around the tape on the balloon.