The Invisible Cushion
Build your own science equipment from a piece of card and a straw, then use it to make a ping pong ball do something that looks impossible. No magnets. No tricks. Just air — and a principle that also keeps planes in the sky.
5-12 yrs
Easy
10
min
Stage 1-3
Mission Briefing.
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Mackey
>
The Invisible Cushion
-
NESA Accredited Teacher
-
High school chemistry & physics specialist 30+ years
-
The Crazy Scientist in primary schools — 15 years
-
International conference presenter on science education
-
Creator of the LAB™ Learning System
-
Curriculum aligned: NSW Science & Technology K–6 (2024)
A picture is worth a thousand words — check this out and see if you can spot the science hiding in plain sight.
Mission Equipment
1 piece of card or thick paper — A4 or larger
1 bendy straw
Blue tack or sticky putty
Scissors
Tape — to hold the cone shape
1 ping pong ball
Optional: coloured markers to decorate your cone
Let’s Investigate
1
Make your cone
Take your piece of card and roll it into a cone shape — wide at the top, narrow at the bottom.
The wide opening should be roughly the size of your palm. Tape along the seam to hold the shape.
Trim the wide end with scissors so it sits flat. Decorate it if you like — this is your science equipment.
3
Prediction time
Hold your cone with the wide end pointing upward. Place the ping pong ball gently on top of the wide opening — it should sit in the opening lightly.
Before you blow: what do you predict will happen when air rushes up through the cone? Will the ball shoot up into the air, hover in place, or fall off the side? Write it down.
5
Tilt the cone
While blowing steadily, slowly tilt your cone sideways — 10 degrees, then 20, then 30.
How far can you tilt it before the ball finally falls?
What is keeping the ball in the airstream even when it is no longer pointing straight up?
2
Fir the straw & cone
Use your scissors to carefully poke or cut a small hole in the very tip of the cone — just big enough for the short end of the bendy straw to push through snugly.
Push the short end of the straw through the hole from the outside. Press blue tack firmly around the straw where it meets the cone tip to seal any gaps.
4
Blow & observe
Hold the cone steady with one hand, and blow a long, continuous breath through the long end of the straw.
Watch what happens to the ball. Try to nudge the ball sideways with your finger while still blowing — then let go. What does the ball do?
6
No cone challenge
Can you levitate the ball using just the bare straw — no cone at all?
Point the straw straight up and try to balance the ball above the opening. Is it harder or easier
Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!
The Crazy Scientist LAB Learning System™
Every experiment follows The Crazy Scientist Lab Learning System™ — a simple way to help kids think like real scientists.
We
-
LINK to what they already know,
-
ACTIVATE curiosity through hands-on discovery
-
BUILD understanding that actually sticks.
Drop a ball — it falls. Every time. Gravity doesn't take days off.
Now think about what would need to happen for a ball to hover in mid-air without being held, without a string, without a magnet.
What could possibly balance the downward pull of gravity without touching the ball at all?
You have a straw, a cone made of card, and a breath of air. That's it.
Predict: when you blow air upward through the cone, what will happen to a ping pong ball sitting above the opening?
You have blown through the cone. Think back — what happened in the first second? Describe it exactly.
When you nudged the ball sideways and let go, what did the ball do? Did it stay where you pushed it, fall, or return?
If the ball returned to centre on its own — something must have pulled or pushed it back. What force did that, and where did it come from?
When you tilted the cone, the ball stayed in the stream past the point where gravity should have pulled it away. What was competing with gravity — and winning?
Fast-moving air has lower pressure — Bernoulli's Principle. The still air around the ball pushes it into the low-pressure zone and keeps it there. And when it drifts, the Coanda Effect bends the airstream to follow it and pulls it back.
A helicopter hovers using spinning blades that force air downward. The same pressure difference holds it up. How is that similar to your cone experiment — and what is different?
"Want the full teacher guide? The Crazy Scientist Lab includes classroom delivery tips, how to manage the WOW moment, differentiation for Stage 2 & 3, — ready to teach tomorrow."
Think Like a Scientist
Scientists don't just do ONE experiment; they change one part of the experiment (independent variable) and then see how it affects another part of the experiment
(dependent variable)
Change ONE variable and test again.
Does the width of the cone's opening change how easy it is to keep the ball hovering — does a wider cone give more control?
What happens if you use a smaller or lighter ball — does the Invisible Cushion work better or worse?
🧪 Try it! Change ONE thing and test again. What did you discover?
Dr Puddledrip’s Science Tip
Want to go deeper? Tap a section below to explore. ▼
The Science Behind It
When you blow through the straw, you create a fast, narrow jet of air that shoots up through the cone and out the wide opening. Fast‑moving air behaves differently from still air: it has lower pressure. In physics, when air is in a hurry, it stops pushing sideways. The still air around it does not — it presses inward with full force.
The ball sits right in the middle of this pressure difference:
Low pressure in the fast airstream
Higher pressure from the still air around it
Gravity pulls the ball down. The upward push from the surrounding air pushes it up. When these two forces balance perfectly, the ball hovers — resting on an invisible cushion of air.
Why the ball doesn’t fall out when you nudge it?
Here’s where the experiment becomes more than just Bernoulli. When the ball drifts sideways, the airstream doesn’t let it escape — it bends to follow the ball’s curved surface. This is the Coanda Effect: moving air clings to curved surfaces and follows their shape.
When the ball drifts right:
the airstream clings to the right side
the air curves away
pressure drops on that side
higher pressure on the left pushes the ball back
The ball self‑corrects — automatically, instantly, and continuously. It’s a built‑in stabilising system. That’s why the ball stays in the stream even when you tilt the cone sideways: the airstream hugs the ball no matter where it drifts.
Why this tiny setup demonstrates real aerodynamics
Aircraft wings, helicopter rotors, hovercraft skirts, and industrial spray nozzles all rely on the same two principles working together:
Bernoulli gives the pressure difference
Coanda gives the steering and stability
Your paper cone and straw are a miniature flight laboratory.
Try next
To see the Coanda Effect working with water instead of air — and pulling a solid object toward a stream rather than holding one above it — try [The Water Magnet]. And if you want to scale this experiment up dramatically, [The Gravity Battlefield] applies the same physics to a balloon and a hair dryer, with a result that is much harder to ignore.
Extension: G&T Years 5 & 6
Why does fast air have lower pressure?
Bernoulli’s Principle explains that when air speeds up, its pressure drops. At the molecular level, fast‑moving air molecules are racing forward, not sideways.
Fewer sideways collisions mean less sideways push — lower pressure.
The ball hovers because the still air around the airstream pushes inward more strongly than the fast air beneath it pushes outward.
Question: If you blew twice as hard, what would happen to the pressure inside the airstream — and how would that change the height of the hovering ball?
Vocabulary
Bernoulli’s Principle: Fast‑moving air has lower pressure than still air. The ball hovers because higher‑pressure air around the airstream pushes inward.
Air pressure: The force of air pushing on a surface. Still air pushes harder sideways than fast‑moving air.
Airstream: A focused flow of moving air. The ball rests on a rising airstream created by your breath through the straw.
Know a parent or teacher who'd love this? Send it on! 👇
READY TO TEACH THIS
TOMORROW?
Running the experiment is easy; however, teaching it well is another challenge.
Teachers often ask:
How do I adapt this for Stages 1,2 or 3?
What do I do with fast finishers?
What misconceptions will they have?
How do I structure this for a full class?
What syllabus outcomes does it cover?
What do I say when they ask WHY?
BUILD AROUND THE LAB LEARNING SYSTEM™
Every resource is designed using our teaching framework.
Inside The Crazy Scientist LAB
Everything you need to confidently teach science tomorrow.
Opening January 2027. Join the Founding Member Waitlist
Try Another Crazy Experiment
Keep the science going with these fun experiments
Let's Go!
Keep exploring with The Crazy Scientist
Hands-On Science Workshops
Interactive STEM experiences aligned to the NSW syllabus.
