how to calculate spring constant if 2 compression spring added together?

Answer 1

The answer depends on whether the springs are added in parallel like this:

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or in series like this:

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If they are in series, then we know that any load (compressive or tensile) must pass through both springs. From this, we can calculate and effective spring constant by looking at how each spring compresses.

P=k1x1=k2x2 where k1 and k2 are the spring constants and x1 and x2 are the displacements of the springs. If we solve for xtot =x1+x2, we find that:

P=xtot/(1/k1 + 1/k2)

In the case of parallel springs, we know that the delta x on each spring is the same, and the load is distributed as the ratio of the stiffnesses. From this, we can write:

x1=x2=xtot

and P1+P2=Ptot

from this and Hooke's equation:

Ptot=x1k1+x2k2 but since x1=x2=xtot

Ptot=(k1 + k2) xtot

Hope that answered your question. Throw a couple of dashpots in next time and it will be a lot more fun!

Answer 2

Spring constants are given in Newtons / meter, yes?

Answer 3

add the constants together