Elasticity

When you stretch a rubber band and let go, it snaps back to its original shape. This ability is called elasticity. Many materials are elastic. They can be pushed, pulled, or squeezed and then return to normal. Springs, trampolines, and bouncy balls all use elasticity.

How Elasticity Works

Inside elastic materials, the molecules are connected by forces that act like tiny springs. When you stretch the material, the molecules get pulled apart. When you let go, the forces pull the molecules back to where they started. The material returns to its original shape.

Elastic Limits

Every material has an elastic limit. If you stretch something too far, it will not spring back. It changes shape permanently or even breaks. A rubber band stretches and returns, but pull it too far and it snaps. Steel is elastic in small amounts but will bend if pushed too hard.

Fun Facts

• Spider silk is one of the most elastic natural materials, stretching up to 40 percent before breaking.
• Steel is actually elastic. Skyscrapers sway slightly in the wind and spring back.
• A trampoline uses the elasticity of stretched fabric and springs to bounce you up.

Did You Know?

Silly Putty is interesting because it behaves differently depending on how fast you stretch it. Pull it slowly and it stretches like taffy. Pull it fast and it snaps like a solid. Roll it into a ball and it bounces!