Proportional limit

Okay kiddo, imagine you have a big balloon and you blow it up slowly. At first, the balloon is pretty small and squishy, so you could keep on blowing it up a little bit without it breaking or popping.

But then, if you blow too hard, the balloon gets too big and BOOM! it pops.

The point where the balloon couldn't take any more air and it popped is like the "proportional limit" of a material. It's the point where if you put any more pressure or tension on the material, it will start to deform or break.

So, just like how you have to be careful when blowing up a balloon, materials have a limit where they can't handle any more stress or strain without breaking. This is called the proportional limit, and it's an important concept for engineers and scientists to understand when designing things that need to be durable and strong.