Why do springs behave like they do?

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Springs are made up of atoms. Those atoms interact with each other as if they are connected by imaginary springs (or so I’ve heard). Here’s the question: what is so special about that helical spring shape that replicates the behavior of atoms on a larger scale?

In: Physics

3 Answers

Anonymous 0 Comments

Springs rely on a material property called elastic deformation. When you push on a material it compresses slightly and then goes back once you so pushing. Exactly how much it compresses depends not only on the material, but the shape as well. There are a bunch of properties that can be designed into a spring, but the biggest one is that a spiral allows the spring to deflect way easier and further than a solid piece of metal would.

Anonymous 0 Comments

Atoms don’t really act like they’re connected by springs. Atoms’ connections are not very linear in their force response. That is to say that, beyond pushing against you when you try to move them, atomic bonds don’t actually act much like springs. That said, helical springs do something very cool – they generate a nearly linear force curve. Every inch you stretch a spring increases its force by roughly the same amount. This is because its helical shape allows it to take advantage of something called local linearization. This is to say that for most normal graphs, if you zoom in enough, the line looks straight. When bending a wire, the force it generates compared to how far it bends is a curve. By coiling this wire up so a lot of it bends a little bit even when the end of the coil is moved substantially, you are effectively zooming into this curve enough that it looks linear or ‘straight’. This is cool because it allows for near-harmonic oscillation, which is used for timekeeping.

Anonymous 0 Comments

Disagree with other answers here: atoms really do behave like they’re connected by springs. In particular, if they’re only moved a short distance, the electric force between them changes in proportion to the amount they move: they obey [Hooke’s Law](https://en.wikipedia.org/wiki/Hooke%27s_law) on an atomic scale. Of course, if you move them a *large* distance, the forces change in complicated ways, but that’s part of why springs have the shape they do.

A solid piece of metal is just a network of atoms joined together so the “springiness” of each atomic bond adds up to springiness of the whole piece. The problem is, the force between atoms is really strong, and the distance you can stretch the atomic bonds before they stop being springy is really small. If you just pull on a steel bar, it *will* stretch, but it’ll take a hell of a lot of force, and it’ll stretch only a tiny bit before it snaps. Springs are designed to get the most macro-scale motion from the least micro-scale stretching.

Springs don’t have to be helical. In particular, flat springs (just thin sheets of springy metal) are very common: the clip on a pen is an example. Since they’re long and thin, a tiny amount of bending at each point gives a pretty big movement overall. But flat springs take up a lot of space. Helical springs are designed so a tiny twisting motion at each point on the spring leads to a big change in length, and so the whole thing fits in a small compact package.