Collapsing Tent

Tonight I was remembering a summer when I was part of an expedition to dig dinosaur bones in South Dakota. We set out tents up on top of the bluff, where we would have a nice view of the area and because it was very close to the bone quarry. While we were at the quarry digging, the wind came up and our tents were blown quite a ways down the hill. It only took us three trys to give up and move our camp down into a ravine. At least we found lots of dinosaur bones.

This experiment shows some of what was happening with those tents. We will learn about Bornoulli’s Principle, and we are going to use it to keep our miniature tent from blowing away.

You will need:

  • a piece of paper about six inches square

Fold the paper in half and crease the fold. Unfold it and place it on the edge of a table, so that it resembles a tent. Before you actually try this experiment, think about what you expect to happen. You are going to blow very hard into the inside of the tent, trying to blow the paper away. Do you think you can do it? Try and see.

What happened? Instead of blowing away, the tent flattened out. The harder you blow, the more stubbornly the tent holds its ground. Why? According to Bornoulli's Principle, fast moving air produces less air pressure than slow moving air. Blowing inside the tent reduces the air pressure on the inside. This lets the higher outside pressure push the tent downwards. The harder you blow, the lower the inside pressure and the harder the outside pressure pushes down.

Why didn't my tent do the same thing at the dinosaur quarry? The tent was closed, and the air was moving faster on the outside. The pressure on the inside was greater and it lifted the tent into the air so it could blow away.