The Physics
Hypertextbook
Opus in profectus

# Springs

## Summary

• The change in size or shape of an object is called deformation and the force applied that causes these changes is called a deforming force.
• If a material tends to return to its original size and shape after a deforming force is applied and then removed, the material is said to be elastic (steel, for example).
• If a material tends to deform permanently after a deforming force is applied and then removed, the material is said to be plastic (wet clay, for example).
• If a material tends to fracture while a deforming force is applied, the material is said to be brittle (concrete, for example).
• All solid materials are elastic as long as the deforming force is less than the elastic limit for the material.
• A spring is…
• a mechanical device whose function depends primarily on it having elastic properties
• a component in a machine used to apply a known force or to store energy
• typically made of coiled steel
• Hooke's law for springs…
• states that the deforming force applied to a spring is directly proportional to its change in length

F ∝ ∆x

• can be written as the equation

F = −kx

where
• k
• is known as the spring constant (because it is a quantity that varies between springs)
• has the SI unit newton per meter [N/m] but variants like the newton per centimeter [N/cm] or newton per millimeter [N/mm] are also common
• x = x − x0
• is the change in length of the spring from its equilibrium length, relaxed length, or natural length x0 to some new length x.
• is described as an extension or elongation when x > x0
• is described as a compression or contraction when x < x0