Spring constant of Achilles tendon

[tag16]

Homework Statement

(a) If the length of the Achilles tendon increases 0.51 cm when the force exerted on it by the muscle increases from 3400 N to 5800 N, what is the "spring constant" of the tendon?
1Your answer is incorrect.
(b) How much work is done by the muscle in stretching the tendon 0.51 cm as the force increases from 3400 N to 5800 N?

Homework Equations

Fx=-kx
k=f1/x1

The Attempt at a Solution

I'm stuck on part a, I used k=f1/x1=(3400/0.51) to find the spring constant but got the wrong answer.

 

[LowlyPion]

Check your units.

.51 cm = .0051 m

Also

ΔF = -kΔx

 

[RoyalCat]

Do you know by how much the spring elongated under the effect of 3400N, or under the effect of 5800N, or do you only know the difference between the two elongations?
Remember that the ratio between the elongation of an ideal spring and the force exerted on it is linear.