Forces can change shape — Physics, 4–6 years
A squeeze, pull or twist can make something look different, and some materials return to their old shape.
Idea
When you squeeze, stretch or twist something, its shape can change. A sponge stays squashed for a moment, while a rubber band pulls back when you let go. The same action can have different results with different materials.
Why
People noticed that clay, wood, cloth and rubber do not respond in the same way when worked. Knowing this helps us choose the right material: clay can be shaped, cloth can bend, and rubber can stretch without breaking straight away. It also helps us make safe toys and tools.
Try it
Take a sponge and a rubber band. First press the sponge with one finger and count to three; it becomes flatter, then grows back when released. Next pull the band between two fingers; it gets longer. Let go carefully, and it returns near its first length.
A common mistake
It is easy to think that every object goes back to its old shape after being bent. That seems reasonable because a rubber band does it. But a paper straw may stay bent, and clay keeps a new shape, so the material matters.
Outside school
This idea is used when people choose materials for everyday things. A raincoat must bend, a hair tie must stretch, and a chair should keep its shape when someone sits down. Designers test materials so objects work well without breaking.
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