Rocket squeezes a flat playground ball. It squishes like a pillow.
Then he squeezes a full one. It pushes back hard!
"Both balls look the same," he says. "Why does one push back?"
Raven taps the full ball. "What do you notice? What is different inside?"
Nova circles the balls. "Think about tiny bits of air," she says. "What do they bump into?"
Air is a gas. A gas fills up whatever container it is in.
Air is made of tiny bits called molecules. They are too small to see.
The molecules zoom around and bump into the walls of their container.
Each bump is a tiny push on the wall.
Huge numbers of tiny pushes add up to air pressure.
Press on a full tire. Your thumb pushes in.
The air inside pushes out.
If the air pushes out as hard as you push in, nothing changes.
If you push harder than the air, the tire dents.
A tire with less air dents more easily.
| Statement | True or false? |
|---|---|
| Air pushes on every part of the tire wall. | ? |
| Air is too small to push on anything. | ? |
| A tire with less air dents more easily. | ? |
| Adding air makes the air push out less. | ? |
| Ball | Did it dent a lot or a little? | Did it push back hard or soft? |
|---|---|---|
| firm ball | ||
| soft ball |
Super squeezing! Tomorrow we learn to read the secret numbers on the side of a tire.