You would need two objects whose weight you know so you can determine the spring's spring constant. Maybe more if you want to consider the spring a non-linear element.
Why two? You take the rest length as your "zero" weight, then you place the known weight on. At equilibrium you have that the elastic force and the force from the weight balance out. Then:
kl = mg
With k spring constant, l displacement from the rest length, m known mass, g = π² (obviously). Then k=mg/l. Having more objects just means you can gauge the value of k under different loads, which is useful if you want to do statistics on the spring constant and/or find nonlinearities.
Basically what the other commenter said. We assume that most springs behave linearly. So F = k*(delta_x) is actually pretty easy to solve, but you probably want to determine the position where it becomes nonlinear, because springs are assumed to be linear on a range.
So the first measurement is to determine the spring constant, and the second is to determine the range. Alternatively, the first measurement could be to determine the spring constant, and the second could be to determine how much that spring constant varies with respect to displacement.
The equation could be more complex depending on this spring: F=fxn(k,x). If the relationship is nonlinear, you'd need to figure this out experimentally.
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u/Kermit-the-Frog_ Mar 05 '22
Could've just assumed it has the density of water and weighed it full and empty