F = kx, F is stretch, k is the stiffness coefficient, x is the length of the elongated spring
For example, to test a 5N spring:
Pull force with 5N stiffness coefficient of 100N / m in the spring, the spring is stretched 5cm
F = kx, k is the stiffness coefficient (in units of Newtons per meter), x is the elongation of the spring (in meters), it is called the law of Hooke's law
For example:
When a spring tension by size 10N, total length of 7cm, when the subject of size 20N tension, total length of 9cm, seeking original length when the force and elongation 3cm size