# Spring Stretching/Compression

## Main Question or Discussion Point

Does it take the same amount of force to compress a spring 1cm as it does to stretch it 1cm?

Is it dependent on the type of spring?

If so, what kind of spring would exhibit properties similar to what I have posted above?

Is the spring constant, k, where F= -kx only used for spring compression, or can it be used interchangeably for both spring stretching and compression?

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tiny-tim
Homework Helper
welcome to pf!

hi gobbledygook! welcome to pf!

in exam questions, springs always obey Hooke's Law (F = -kx)

and yes it applies to both stretching (extension) and compression

(whether it applies accurately to all real-life springs, i have no idea! )

AlephZero
Homework Helper

(whether it applies accurately to all real-life springs, i have no idea! )
It doesn't. It is true for many types of real-life springs, but you can make the relation between force and displacement pretty much anything you like by designing the right sort of spring.

One example of when it isn't true a long coil spring that would "buckle" when you try to compress it, and the force needed to compress it would be very small.

Another example is a coil spring that is made with the coils touching each other, so you can't compress it at all, but you can stretch it easily.

But tiny-tim is right - you can assume it is true in physics or engineering "homework" type questions, unless the question tells you to assume something different.

Thanks Tim!

I am actually trying to find the spring constant of the launcher that I built.

Here are some photos of my spring launcher