Answer:
37.4 cm
Step-by-step explanation:
The force that the spring exterts when stretched is:
![F = -k (x-x_0)](https://img.qammunity.org/2020/formulas/physics/high-school/wmp1rcpno279snvfre2ohl6vepzaob5mv8.png)
Where x_0 is the relaxed length and k = 680 N/m
If a steady force of 133 N is applied when pulling the spring and elonged to a total length of 57 cm, the spring must extert the same force, but in the opposite direction, that is:
![-133 N = -680 N/m (0.57m -x_0)](https://img.qammunity.org/2020/formulas/physics/high-school/pz69hsbku22a3rsph47qkgt3tv3cbf4bac.png)
Solving for x_0
![x_0 = 0.57 m -(133)/(680) m = 0.57 - 0.196 m = 0.374 m](https://img.qammunity.org/2020/formulas/physics/high-school/2hm3m3seuc4u6iia87lrq9pc9p9ow88klb.png)