Spring constant k or the force constant of an elastic spring is defined as the force required for elongating it by a unit length.
F = k x and k = F / x
x = the displacement of the tip (end) of the spring from its equilibrium normal position.
F = force required to displace the tip (end) of the spring by x length.
the values of k are very small for a rubber band we use at home.
They are high for strong springs.
