This morning we worked hard to get our Math, Language, Grammar, and Writing subjects finished up so we could meet up with our friends at the Batawa Dino Dig this afternoon. We enjoyed digging up a huge dino skeleton, looking at fossils, and going on a nature trail where we spied a snake eating a frog!
When we got home, we read our History lesson for today about Mary Queen of Scots, then finished up our day with a science lesson about how birds wings work and air pressure.
Here is a fun experiment that shows you how air pressure works.
You will need a cup completely full of water, two straws, and scissors.
Put one straw in the water and cut it so that it sticks out of the water by only about ½ inch.
Now, put the cup with the straw in it next to the edge of a counter or table, and squat down so your eyes are level with the cup. Using your fingers to hold the small straw next to the edge of the cup, blow through the other straw at an angle towards the top of the straw in the cup. Angle the straw upwards so that the air coming out of it passes right over the top of the straw in the cup. Keep blowing and blowing. This will make the air move faster over the top of the straw in the water. As a result, the air pressure above the straw in the water will decrease, and when there is less air pressure above the straw, what do you think will happen? Try it and see.
Did a stream of water squirt out the straw that was in the cup? It should have, if you blew at the right angle. Be sure you weren’t trying to blow on the water in the cup; blow only on the tip of the straw in the cup. Keep trying until it works.
What explains this result? Well, when you blew air over the top of the straw, the moving air could not press down as hard on the water in the straw. The air over the rest of the water in the cup was not moving, so it continued to press down on the water with its full pressure. Since the water in the cup was being pressed down harder than the water in the straw,water was forced up and out of the straw! This is a lot like what happens to a bird’s wing. Just as the difference in air pressure over the straw and the rest of the cup lifted water out of the straw, the difference in air pressure between the top and bottom of a bird’s wing lifts the wing into the air.