Blog

You will need

• A4 paper
• Wide-mouthed bottle, e.g. sports drink or iced tea bottle
• Small hardcover book

What to do

1. Tear or cut the paper in half, and then scrunch one half into a tight ball.
2. Check that the ball fits easily through the mouth of the bottle. If it doesn’t, take the ball and scrunch it more tightly until it’s small enough. If it still doesn’t fit, unscrunch the ball, rip off some of the paper and scrunch it up again. Make sure the ball now fits easily through the mouth of the bottle.
3. Put the ball on the book, near the edge.
4. Place the mouth of the bottle near the ball.
5. Put your mouth near the other side of the book and try to blow the ball into the bottle. Did it work?

What’s happening?

It’s really hard to get that ball in the bottle. To understand why, we’ll have to think about what’s happening to move the ball.

When you blow on the paper ball, you’re not just giving it a push. Instead, it’s more like you’re making a gust of air, and the ball is coming along for the ride.

When you try to blow air into the bottle, there’s a bit of a problem. The bottle is already full of air, and the only way out is through the mouth. Since the ball is quite wide, there’s not enough room for air to go in and out of the bottle at the same time. Instead of going into the bottle, your breath goes around and the ball stops right at the mouth of the bottle.

There are still ways to get the ball in. A short, sharp gust of breath can get the ball rolling, and if it’s moving fast enough and there’s no breath blowing around, the ball should be heavy enough to push a ball-sized amount of air out of the bottle.

Using a smaller ball also helps. A smaller ball means there is more space around the ball for air to come out of the bottle. With a very small ball and a tight stream of air from your mouth, it’s possible to get the ball into the bottle!