Where are spring-mass systems used in real life?

[MathWarrior]

I was wondering, in my class we have been dealing with a lot of equations related to some weight attached to a spring which is attached to a fixed point and has some force being applied to it or something like that. Where exactly is such a thing encountered in real life?

 

[tiny-tim]

lots of weighing machines

things like car suspensions (except upside-down)