Make a balloon hovercraft : Fizzics Education

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# Make a balloon hovercraft

### You will need:

• A CD that you don’t mind being wrecked
• A pop-top bottle lid (sports drinks & various juice companies sell bottles with these lids)
• A balloon
• A hot glue gun and adult supervision
• A4 paper or mat that you can do craft on
• Safety glasses

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Use the hot glue gun to connect the pop-top bottle lid to the CD. Make sure that you keep this lid centred to the CD as much as possible.

2

Once the hot glue has cooled and dried, press the sports drink lid down so that the valve is shut inside the lid.

3

Blow up a balloon and then attach it to the pop-top bottle lid.

4

As the valve is closed, the air should not rush out of the balloon whilst attached to the lid.

5

Open the lid valve and give your balloon hovercraft a little push. You should see it glide across the desk easily!

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### What is going on?

You reduced friction!

Friction is the force that exists between two objects and is influenced by the amount of contact between the two surfaces as well as the pressure between them as well. Friction always acts in the opposite direction to movement and causes objects to slow down.

The air thrust from the balloon pushes the hovercrafts mass away from the table, thereby reducing the friction between the CD and the table. Your balloon hovercraft continues to be able to slide across a desk or smooth floor as long as there is enough air pressure in the balloon to hold the CD up from the surface. This simple experiment is just a miniature version of water occurs with commercial hovercrafts whereby industrial fans introduce tremendous amounts of force to hold up the hovercraft.

Contact with the ground is essential for tyres to be safe, allowing you to control your vehicle. The tread of your tyre is designed to disperse water whilst keeping your tyre in constant contact with the road. The greater the contact, the great the frictional forces. You can lose control of your vehicle if lose contact, and therefore friction, with the road. This often occurs when a car aquaplanes, whereby water is forced under the wheels which reduces tyre contact to the road and reduces your ability to steer or brake your vehicle.

### Variables to test

• Does the size of the balloon matter?
• What happens when you make the surface rougher?
• Can you create the same effect with something other than a CD?
• How large can you make it?

Hovercraft being used during a Fizzics science show!

### Going further

Liquids can slide on pockets of gas too. During our liquid nitrogen show, we demonstrate the Leidenfrost effect which in a way emulates hovercrafts… however in this case we show rapidly boiling liquid nitrogen droplets sliding along a smooth surface due to the gas trapped beneath each droplet caused during the rapid boiling.Â  This can be quite a spectacular effect!