
`stiffness` is the name of a spring's `k` input on [iOS](https://developer.apple.com/documentation/quartzcore/caspringanimation), [Android](https://developer.android.com/topic/libraries/support-library/preview/spring-animation.html), and the [Web](bbc0f831e2/src/index.js (L11-L22)
). To ensure the API is familiar to and easily understood by developers coming from other platforms, Flutter should follow this convention as well.
This is a minimally-breaking change. Across [all of GitHub](https://github.com/search?l=Dart&q=springConstant&type=Code&utf8=%E2%9C%93), there are only 2 uses of the `springConstant` API (in Mondrian). Those can be easily changed to use this name.
Closes #11684