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Hans Christian Andersen - The Snow Queen
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# 23/01/2013

Mel Giedroyc continues listening to our wonderful story, MM Kaye's 'The Ordinary Princess' and the Inheritance Tracks of legendary singer, songwriter and activist, Harry Belafonte.

1 hour

## Last on

Wed 23 Jan 2013 16:00

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## Activity 1: Paper planes

You can explore aerodynamics by making different paper planes. All you need is some A4 paper. In the programme, Dom’s plane flies the furthest, so we’ll give you the instructions to make his version.

Fold the paper in half lengthways, and then unfold again, so you have a line across the middle of your sheet. At the end you want to be the front of your plane, take the corners, and fold them so they meet the crease in the middle, giving you a point at one end, with the folded over bits of paper making a triangle shape.

Taking the points of the triangle which meet the straight edges of the paper, fold the paper over to meet the crease in the middle again. Your paper should be looking very pointy now, with a short length at the non-pointy end left unfolded.

Now, turn your paper over, and fold the long sides down to meet the middle crease.
Turn it over again, and go over the very first fold you made down the middle again, to give your plane shape. You’re nearly there!

Finally, at the back of your plane, take the very short edges that haven’t yet been folded over, and fold them up about a centimetre, so you have some tailfins. Your Dominic Wood style paper plane is ready to fly!

Do you have any other favourite designs for making a paper plane. How do they compare? What happens if you try folding a plane with bigger wings, or if you put some kind of weight, such as paper clip, on the nose?

## Activity 2: The Bernoulli Effect

The Bernoulli Effect, named after a Swiss scientist, is one of many things which contribute towards keeping a plane in the air. Here are two demonstrations which show the Bernoulli Effect.

Take a piece of paper, and fold it in half, so it looks like a book. Next, you need to make a spine. Take one half of the paper, and starting about half a centimetre from the original fold, fold it back over on itself, so the paper is open again, but overlapping in the middle. Turn it over, and do the same on the other side. What you should end up with is a little bit like a paper plane – with a central fold you can hold, and two flaps on either side.

But for this activity, you want to hold your paper the other way round from a plane, so that the spine is at the top, and the flaps are hanging down, like a paper seagull, or a tent shape!

What do you think will happen when you blow between the flaps?  Will they open out more, or will they close?

What’s happening?
Try it – you should see the flaps of paper close. When you blow, you are creating an area of low pressure. When you create that low pressure inside the flaps of paper, the higher pressure air from outside pushes on the flaps, and they move inwards.

An aeroplane’s wing is designed to take advantage of the Bernoulli Effect. The shape of the wing means that the air on top of the wing moves faster than the air underneath, creating a lower pressure, and helping to lift the plane into the air.

Another way to see the Bernoulli Effect moving air from one place to another is to use a lightweight polythene tube, such as the bags which are used in some nappy disposal systems.  You need a length about a metre long. Tie a knot in one end.

How many breaths do you think it will take you to fill up the bag? And did you know it can be done with just one breath?

Stand a bit back from the tube, and open it out. Take a deep breath, make your mouth into a shape as if you were about to whistle – and blow a strong and direct stream of air into the centre of the open tube.  The tube should fill with air.

What’s happening?
When you blow into the tube, you create an area of low pressure air. High pressure air will follow low pressure air – so the air from outside the tube, in the room, will go into the tube along with the air from your lungs, inflating it all in one go.

## Activity 3: Marshmallow cabin pressure

In an aeroplane, the cabin that people travel in is pressurised, because high up in the air, the air pressure is a lot lower than what we’re used to down on the ground. Here, you can see the impact of low pressure on some sugary treats.

You will need:

• Marshmallows
• flour
• An empty clear wine bottle
• A wine saver vacuum pump and stopper

In order to fit the marshmallows inside the wine bottle, cut them in half. They’ll be sticky, so to make sure they don’t get stuck in the neck of the bottle, roll them in a bit of flour first.
Then, push the marshmallows into the bottle. Place the stopper in the bottle, and use the vacuum pump to remove some air from the bottle. Watch what happens to the marshmallows… they should get bigger, and bigger... When you remove the stopper from the bottle, they’ll return to their normal size.

What’s happening?
When you remove some of the air from the bottle using the pump, you’re reducing the air pressure  (the push of the air) inside the bottle. But inside the marshmallows there are lots of tiny air bubbles and the pressure of the air in these bubbles doesn’t change. The air inside the marshmallows now has more push than the air outside the marshmallows, and so the air inside the marshmallows pushes outwards. This causes the marshmallows to get larger and larger.

When you take the stopper off and let the air back into the bottle, the pressure returns to normal, and the marshmallows will deflate back to their original size.