DENJIRO: Do you know what this is? It's called a slingshot. It shoots balls using the force of the rubber when it stretches and contracts. Now, let's try it out.
The ball flew at a great speed. The force that made the ball fly is called rubber elasticity, a unique feature of rubber in which it stretches and contracts.
Now, I'll explain the mechanics behind rubber elasticity. The molecules in rubber are long and connected together. Those particles go through thermal motion, which causes the stretching and contracting. As the temperature rises, the rubber elasticity becomes stronger. And as the temperature drops, the rubber elasticity also drops. Let's use liquid nitrogen at -196 degrees Celsius to test this out.
Here, we'll take a rubber band, stretch it out using two glass rods, and place it in the liquid nitrogen. It froze in its stretched state. Here's a rubber band stretched out in the shape of a star. After we put it in the liquid nitrogen, we'll take it off of the glass rods. As you can see, the rubber stays the shape of a star. The rubber is not able to shrink back to its original shape because the rubber elasticity has dropped. When we take it out of the liquid nitrogen, it goes back to its original shape because it gets warmed up and regains its elasticity.
Here, we have a special slingshot. Let's fire this rubber ball using elasticity!
MAN: 3,2,1, fire!
DENJIRO: The ball shattered into pieces! It was cooled down using liquid nitrogen. Due to its low temperature and low elasticity, it shattered like glass.
I hope energy will bring you all happiness. Our magic word is "Happy Energy!"