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Don’t ruin my hair!!!

If you liked our Waterproof Cloth trick on TikTok, here’s a quick explanation of how it all worked.

You wouldn’t think that a handkerchief or a cleaning cloth would make a particularly effective ‘plug’ to stop water pouring out from a glass held upside down. But if you’ve just watched someone on TikTok carrying out this experiment then you’ll know that they really can!

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Don’t ruin
my hair!!!

Woman in the Rain

If you liked our Waterproof Cloth trick on TikTok, here’s a quick explanation of how it all worked.

Tik Tok

You wouldn’t think that a handkerchief or a cleaning cloth would make a particularly effective ‘plug’ to stop water pouring out from a glass held upside down. But if you’ve just watched someone on TikTok carrying out this experiment then you’ll know that they really can!

Here comes the science

When you usually turn a glass of water upside down gravity pulls down on the water which makes it pour out of the glass. But in our experiment, other invisible forces – upward air pressure and surface tension – stop the water from coming out of the glass. Air pressure pushes on everything, so pushes up through the mouth of the upside down glass. Surface tension is what gives water an elastic-like skin.You know how you can overfill a glass just above the top without it spilling? Well, that’s surface tension.

The strength of surface tension varies. The smaller the stretch of water across a gap, the stronger the surface tension. Without a cloth, the hole at the top of a glass is large and the strength of the surface tension and upward forces of air pressure aren’t big enough to beat the downward force of gravity.

But when you place a cloth – which has loads of tiny holes in it – across the top of the glass, the holes through which water has to go are much smaller so the surface tension is a lot stronger. This super strong surface tension, combined with the upward push of air pressure, is large enough to balance the force of gravity and keep the water inside the glass. There’s no real magic at play here but there are some amazing things going on which can be explained by physics!!

Want to experiment more?
If you liked this YoutubeWaterproof Cloth trick then you’re well on your way to becoming a physicist. You can also watch our TikTokers carry out an amazing eggsperiment in any of the links below. And there are loads more experiments that you can try at home by watching these videos on YouTube

Eggs are tougher than you think!

We think of eggs as being fragile. They easily crack on the side of the pan. And if you drop one it will smash. So it’s surprising when someone stands on them and they don’t just collapse into a messy gunge of broken shells.

There are two parts that explain what is going on.

Reason #1.
When you stand on the egg box in bare feet, your weight (in physics terms ‘the load’) is shared over all the eggs. So, if you can spread your foot evenly across ten eggs, each egg only has to withstand a tenth of your weight!

Reason #2.
An egg will crack if you tap it on a pan but it is super strong if you try to squash it along its length. This is because eggs are dome-shaped and domes are particularly strong structures.

People have known this for thousands of years and it’s the reason why you see so many domes in old buildings. A dome directs the forces along the length of the material, (literally) playing to its strength. Also, because a dome forms a complete circle, it spreads the load evenly and prevents it from being concentrated in any small areas – stopping anything from cracking. Pretty amazing don’t you think!

Physics in the real world

You love your tech right? But did you know that behind pretty much every bit of technology that we now rely on there’s some amazing physics going on? Touch screens, WiFi, and Bluetooth. None of these things would be possible without an understanding of the physics behind them. If you want to know more then click here.

Our world would be rubbish without an understanding of physics. Almost everything we experience and enjoy involves physics. From staying warm in winter, to riding on a train or bus to see our mates, to eating crispy, even-looking chips from KFC or McDonald’s, physics has a role to play.

And if you’ve ever dreamed about one day going into space…Well without our scientists understanding and explaining the physics going on with rockets you can forget about it!

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Physics for Everyone

Physics is for everyone

We think too many young people drop physics at school too quickly. We know that there’s a view that the other science subjects are less hard and more interesting (or yes, we know it, less nerdy). It’s a sad fact that fewer girls study physics than boys. Fewer students from some ethnic minority groups study it too.

Too many young people are made to feel that they can’t do physics. Maybe you’ve been told ‘you’re not clever enough’, or ‘you’re not male enough’, or ‘you’re not white enough’, or ‘you’re not posh enough’. None of this is true, never was, never will be.

So we say don’t dismiss studying physics at school. Physics opens doors to some of the most exciting, cutting-edge, rewarding jobs in the world – like tackling climate change, gaming, robotics and artificial intelligence. And much, much more.

So go on and seize the opportunities that physics offers you for your future and for your world.

To find out more about this campaign, please visit us at iop.org/LimitLess.

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