The Gravity Battlefield
Gravity pulls everything downward without exception — every ball, every book, every balloon. A hair dryer disagrees. This experiment puts them head to head and lets you decide who wins before you see the result.
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
Alex
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The Gravity Battlefield
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NESA Accredited Teacher
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High school chemistry & physics specialist 30+ years
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The Crazy Scientist in primary schools — 15 years
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International conference presenter on science education
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Creator of the LAB™ Learning System
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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 round balloon — standard size
1 small coin — 10c or 20c
1 hair dryer — set to COOL air, medium speed
Optional: coloured markers to draw a face on the balloon
Adult supervision required when using the hair dryer
Let’s Investigate
1
Prepare the balloon
Before inflating, drop a small coin (10c or 20c) inside the balloon.
Inflate the balloon to roughly grapefruit size — not fully inflated. Tie it off.
3
Switch on the air!
Turn the hair dryer on — cool air, medium speed — and let go of the balloon.
Watch what happens. Try to observe exactly where the balloon settles and what keeps it there.
5
Tilt the battlefield
While the balloon is hovering, slowly tilt the hair dryer sideways — 10 degrees, then 20, then 30.
Does the balloon follow? How far can you tilt the hair dryer before gravity finally wins?
2
Predict
Hold the hair dryer in one hand, pointing straight up, set to cool air on medium speed.
Hold the balloon in your other hand, directly above the nozzle but not touching it.
Before you switch on: what do you predict will happen when you turn the hair dryer on and let go of the balloon?
4
Push it
With the balloon hovering, use a finger to gently push it sideways — then let go.
What does the balloon do? Try pushing it further each time. How far can you push it before it leaves the airstream entirely?
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
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LINK to what they already know,
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ACTIVATE curiosity through hands-on discovery
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BUILD understanding that actually sticks.
Gravity pulls everything downward. Drop a ball — it falls. Throw a balloon in the air — it falls.
The only things that genuinely resist gravity are things that are lighter than air — like helium balloons — or things with engines, like planes and rockets.
A regular air-filled balloon is heavier than it looks. Gravity should win.
But what if moving air could create a force powerful enough to keep a balloon suspended — without touching it, without a string, without helium?
Predict: when you hold a balloon above a hair dryer and let go, what happens? Write your answer — and your reason — before you try.
You switched the hair dryer on and let go. Describe exactly what happened in the first three seconds.
When you pushed the balloon sideways, what did it do when you let go?
Something kept the balloon in place. Was it pulling it from below, or pressing it from the sides? How do you know?
When you tilted the hair dryer, the balloon followed — even though gravity was pulling it straight down. What force was stronger than gravity in that moment?
Fast-moving air has lower pressure — Bernoulli's Principle. The still air around the balloon pushes it into the low-pressure zone. The Coanda Effect keeps it there even when tilted.
A jumbo jet weighs over 400 tonnes. Its wings create lift using exactly this pressure difference — fast air above the curved wing, slower air below. How does a pressure difference create enough force to lift 400 tonnes?
"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 size of the balloon change how stable the hover is — does a larger balloon work better or worse?
Does the coin inside the balloon make a difference — what happens to the hover if you remove it?
🧪 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
Why does the balloon hover instead of falling?
A hair dryer blasts a column of air upward. That air is moving fast. And fast‑moving air has lower pressure than the still air around it. Daniel Bernoulli discovered this in the 1700s: when a fluid speeds up, its pressure drops.
Think of it like a busy motorway. Cars travelling at high speed stay in their lanes — they don’t push sideways. But the still air beside the motorway? It presses in from all directions with full force. The balloon sits right in this situation:
Low pressure in the fast airstream
Normal pressure from the surrounding still air
That surrounding air squeezes inward, holding the balloon inside the rising column. Gravity pulls down, but the pressure difference pushes up harder. The balloon hovers.
Why the coin matters?
A balloon on its own is too light and too symmetrical. It spins, wobbles, and drifts — it has no “down”. Drop a coin inside and everything changes. The coin settles at the bottom, giving the balloon a heavy end and a light end. Now it behaves like a ship with ballast:
the heavy end stays down
the balloon stabilises
the wobbling stops
The coin doesn’t help the balloon float — it helps it stay upright long enough for the air column to catch and hold it.
Why does the balloon follow the airstream when you tilt the dryer?
This is the Coanda Effect — the tendency of moving air to cling to curved surfaces. When you tilt the hair dryer, the airstream tilts too. Instead of falling out of the stream, the balloon “chases” it.
Here’s what’s happening:
The curved surface of the balloon bends the fast air around it.
The air sticks to the balloon’s surface and curves away.
Where the air curves away, the pressure drops.
Higher pressure on the opposite side pushes the balloon back in.
The balloon constantly self‑corrects — always nudged back toward the centre of the airstream. It behaves like a satellite hugging its orbit: drifting slightly, correcting instantly, never escaping.
Where have you seen this before?
The same two principles — Bernoulli and Coanda — work together in:
every aircraft wing
every helicopter rotor
every hovercraft
every leaf that lifts and flutters above a campfire
Your hair dryer just demonstrated the physics of flight using nothing more than a balloon and a coin.
Try next
To see the same self-correcting Coanda behaviour on a smaller scale — and without a hair dryer — try [The Invisible Cushion], where a handmade card cone and a single breath do the same job. And if you want to see Bernoulli working sideways instead of vertically, [The Stubborn Balloons] shows what happens when fast air runs between two objects instead of under one.
Extension: G&T Years 5 & 6
The Coanda Effect — air that clings
The Coanda Effect explains why the balloon follows the airstream when you tilt the dryer. Moving air tends to cling to curved surfaces and bend around them.
When the balloon deflects the airstream, the pressure on that side drops. Higher pressure on the opposite side pushes the balloon back toward the stream. This creates a self‑correcting loop: drift, pressure change, correction.
Question: Can you think of a natural example where air or water “sticks” to a curved surface instead of flowing straight past?
Bernoulli + Coanda = flight Aircraft wings use both principles at once: • Bernoulli: faster air over the wing → lower pressure → lift • Coanda: air curves over the wing’s surface → stabilises the flow
Your balloon is a simplified version of a wing — a flying lesson in slow motion.
Vocabulary
Bernoulli’s Principle: Fast‑moving air has lower pressure than still air. The balloon stays in the airstream because higher‑pressure air around it pushes inward.
Coanda Effect: The tendency of moving air to cling to curved surfaces and follow their shape. This keeps the balloon “locked” into the tilted airstream.
Air pressure: The force of air pushing on a surface. Still air pushes harder sideways than fast‑moving air.
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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?
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