# Why do springs bounce back after being pulled?

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It is interesting how spring-shaped object have this bouncy characteristic quality about them. Even if its hair or just an ordinary spring, they snap back to their original shape. Why is it that corkscrew shapes are so elastic?

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Springs as well as hair and rope all act as springs. Seriously all materials have this property.

However, there is a thing called the elastic limit. The elastic limit is the point where the material permanently distorts.

So with springs, you pull and they don’t snap back, hair breaks although there is a moment before that happens where it would have sprung back.

Try it with a paperclip.

Springiness is a property of matter.
Try looking up Hooke’s law.

https://byjus.com/physics/hookes-law-equation-experiment/

And the Modulus of Elasticity.

https://material-properties.org/what-is-modulus-of-elasticity-elastic-modulus-definition/

It’s not the corkscrew shape that lets springs snap back.

All materials, when bent, have a range of “elastic deformation” – in this range of motion they will return to their original shape. When you overshoot this, you either permanently bend or break something.

A solid metal bar will experience this too.

A coil allows a small bend in the metal to add up down the length of the spring to make a larger bend. This means that no individual point of the spring bends a lot, but they add together to bend a lot. They never bend so much to break or get permanently deformed.

Imagine a thin rod. Anchor one end rigidly, and attach a lever that rotates the bar about its own axis to the other end.

You can use the lever to twist the rod, a bit. If you let go, it springs back. This is a type of spring called a torsion bar.

If you make the rod longer you can twist it more. More elastic. And so on if you make it longer and longer. But very long very elastic torsion bars get cumbersome.

So wind the torsion bar into a cylinder – the cork screw shape as you call it – you now have a coil spring. A very long torsion spring in a small space, gives you that elasticity you see.

It’s not about the shape of the spring, but about the length of the spring.