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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.
From the LAB
What you will need
1 ping pong ball
1 metal spoon
Tape
A tap or faucet with running water
A sink (or large bowl to catch water)
A piece of string (~30 cm) to hang the ball
How to do it
1
Start with a spoon
Turn your tap on to a thin, steady stream — about the width of a pencil.
Hold the back of a spoon (the curved side) close to the stream without letting them touch.
Watch what the water does when it reaches the spoon's curved surface. Does it bounce away — or does something else happen?
3
Place near water stream
Hold it in the air close to, but NOT touching, the running stream. Before you move it any closer: what do you predict will happen?
5
Observe
Once the ball is right beside the stream, relax your fingers a little.
Notice whether the ball tries to move on its own — and what it feels like in your fingers. What is holding it there?
Notice whether the ball tries to move on its own — and what it feels like in your fingers. What is holding it there?
2
Make your ball on a string
Tape a ping-pong ball to a 30 cm length of string.
4
The test
With the ball about 3–4 cm from the stream, slowly slide it sideways toward the water.
Watch carefully — something unexpected should happen before the ball even touches the stream.
Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!
The Water Magnet
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Running water has a secret: point a stream at a curved surface and the surface wins. This experiment reveals one of physics' most surprising tricks — invisible air pressure can make a ping pong ball chase a stream of water across a sink.
5-12 yrs
Easy
10
min
Stage 1-3
>
The Water Magnet
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.
Think about a magnet pulling a paperclip toward it. Now think about water running from a tap — it flows, it splashes, it soaks things.
Water can't pull a solid object toward it from a distance. That's not how water works.
Or is it?
One curved surface is about to change your mind.
Predict: what will happen when you hold a ping pong ball next to a thin stream of running water — without letting them touch? Write it down before you try.
You have run the experiment. Think back to the moment the ball got close to the stream —describe exactly what happened.
Compare what you felt in your fingers in Step 4 and what you saw in Step 5. Were they telling you the same thing?
When the ball was next to the stream, did it feel like it was being pulled by the water, pushed by something else, or held in place by both?
When you used the string, the ball leaned toward the stream — but the stream was hitting one side of the ball. What was pushing from the other side?
Fluids — water and air both — cling to curved surfaces. Scientists call this the Coanda Effect.
The curved upper surface of an aircraft wing forces air to speed up and cling — this creates lower pressure above the wing than below. How does that lift a plane weighing hundreds of 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.
What happens if you replace the ping pong ball with a heavier ball — does the Coanda Effect still work?
Does the thickness of the water stream change how strongly the ball is pulled toward it?
🧪 Try it! Change ONE thing and test again. What did you discover?
Want to go deeper? Tap a section below to explore. ▼
The Science Behind It
Water has a trick up its sleeve: point a fast-moving stream at a curved surface, and the stream refuses to leave. It clings. It wraps. It follows the curve wherever it goes — like a loyal dog that won't let go of a favourite stick.
Scientists call this the Coanda Effect, after Henri Coanda, the Romanian engineer who first studied it in the early 1900s. He noticed that a jet of fluid directed near a curved surface would bend and follow the contour of that surface rather than continuing in a straight line.
At first, this seems like a minor curiosity. Then you realise it explains why your shower curtain billows inward when you're not touching it, why aircraft wings generate lift, and why a ping pong ball refuses to let go of a stream of water from your kitchen tap.
When the water from your tap meets the curved surface of the ping pong ball, it wraps around it — clinging to the surface, following the curve all the way around. This creates a region of lower air pressure on the side of the ball where the water is flowing.
Meanwhile, the still air on the opposite side of the ball is sitting at normal atmospheric pressure — higher than the water-side. Pressure always pushes from high to low, so that pressure difference shoves the ball toward the stream. What looks like the water pulling the ball toward it is actually the surrounding air pressing it in from behind. The water set up the conditions. The air did the pushing.
This is the same principle that keeps aircraft in the sky. The curved upper surface of a wing forces air to travel a longer path — so it has to speed up. Faster-moving air has lower pressure. The higher pressure beneath the wing pushes upward, generating lift. Your kitchen tap just demonstrated the physics of flight, using nothing but a ping pong ball and a spoon.
For another experiment where moving air creates a completely counterintuitive pressure result, try [The Impossible Blow] — where blowing harder keeps a ball trapped rather than pushing it away. And if you want to see the same Coanda logic applied to a pair of balloons, [The Stubborn Balloons] will produce a result that almost nobody predicts correctly the first time.
Extension: G&T Years 5 & 6
Vocabulary
Know a parent or teacher who'd love this? Send it on! 👇
The Crazy Scientist books
These highly visual books combine storytelling and real science, helping students revisit key concepts and stay engaged long after the session.
Designed by a practising NSW classroom teacher (30+ years experience), these books directly support NSW Science & Technology (2024) outcomes and reinforce “Working Scientifically” skills.
Perfect for classroom libraries or home explorations.
For teachers (YouTube)
— Science Before the Bell
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Quick, curriculum-linked science you can teach tomorro
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.
