Liquid That Fights Back
✨ Your finger sinks in slowly like honey, but a fast punch lands on it as if it were a solid floor.
🧰 You need
- two cups of cornflour
- about one cup of water
- a wide bowl
- a spoon
- a tray to work on
⚠️ Do not pour the mixture down the drain, because it can block pipes; put it in the bin.
👀 What you will see
Slow movements let your finger slide right in. A fast tap bounces off a surface that feels almost hard, and hardly any splashes. A ball rolled quickly holds together, then melts back into a puddle the moment you stop.
🧪 Do it
- Put the cornflour in the bowl and add water a little at a time, stirring as you go.
- Stop adding water when the mixture pours slowly but resists a quick stir.
- Dip a finger in very slowly and then pull it out slowly.
- Now tap the surface hard and fast with the back of a spoon.
- Scoop some up, roll it quickly into a ball, then stop rolling and let it sit on your palm.
- Tip the bowl and watch the mixture pour.
💡 Why it happens
This mixture is a suspension: millions of tiny solid cornflour grains sitting in water rather than dissolving in it. When you move slowly, water has time to flow into the gaps between the grains, so the mixture behaves like a thick liquid. A sudden force jams the grains against each other before the water can move, so for that instant the mixture behaves like a solid. A material that changes how runny it is depending on the force is called non-Newtonian, and engineers study such mixtures for body armour and shock absorbers.
🔁 Now try this
Make a second batch with twice as much water and test whether a fast tap still feels solid.
🤔 Think about it
Is tomato ketchup that suddenly rushes out of a bottle behaving in a similar way?
🧘 Ask the Acharya
“Is tomato ketchup that suddenly rushes out of a bottle behaving in a similar way?” — ask him and he will explain it from your own chapters.
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