Find spring force F = k x and elastic energy U = ½ k x².
| Force (N) | – |
| Energy (J) | – |
Use this calculator for a linear spring. k is the spring rate in N/m and x is extension (or compression) from the unloaded length. Force is returned as k x, so it keeps the sign of x; energy ½ k x² is always non-negative. Real springs leave Hooke’s region if you stretch them too far.
k = 200 N/m and x = 0.05 m give F = 10 N and U = 0.25 J. Stiffness must be greater than zero. 5 cm is 0.05 m.
k (N/m): Stiffness. A door spring might be hundreds of N/m.
Extension (m): Change of length from rest, in metres.
Force (N): F = k x, signed like x.
Energy (J): Elastic potential ½ k x².
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