Spring Constant

Spring Constant

Spring constant is a measure of the elasticity of the spring, it is also known as force constant. The higher its value, the more the force we will need to exert to extend the spring. The quantity that specifies the stiffness of a spring is called as the spring constant. Every spring has its own natural value of spring constant. K is the symbol of spring constant, its SI unit is N/m.

Actually, the spring works on the basis of Newton’s third law of motion. It states that “for every action there is an equal and opposite reaction”. The law that gives the relation between this restoring force and the displacement is Hooke’s law. It states that, “the restoring force of a spring is directly proportional to the small displacement”. The constant of proportionality is called the spring constant.

It can be expressed as:

F = – kx


F = Restoring Force,

k = Spring Constant,

x = displacement produced.

The negative sign indicates that the restoring force and the displacement oppose each other.

Now, Spring Constant (k) = Force (F)/ Displacement (x).

It can also be explained as the ratio of the restoring force to the deviation from the equilibrium position. The property by which an object regains its original shape after distortion is known as elasticity. Spring constant represents the amount of fore required to stretch an object. If an object possesses a high value of spring constant, then it is stiffer.

If two springs having the spring constants k₁ and k₂ are connected in parallel, then the equivalent spring constant will be:

k = k₁ + k₂

If they are connected in series, then the equivalent spring constant will be:

k = [(1/ k₁) + (1/ k₂)]⁻¹