Editing Young's modulus (section)

===Force exerted by stretched or contracted material===
Young's modulus of a material can be used to calculate the force it exerts under specific strain.

:<math>F = \frac{E A \, \Delta L} {L_0}</math>
where <math>F</math> is the force exerted by the material when contracted or stretched by <math>\Delta L</math>.

[[Hooke's law]] for a stretched wire can be derived from this formula:
:<math>F = \left( \frac{E A} {L_0} \right) \, \Delta L = k x </math>
where it comes in saturation
:<math>k \equiv \frac {E A} {L_0} \,</math> and <math>x \equiv \Delta L. </math>

Note that the elasticity of coiled springs comes from [[shear modulus]], not Young's modulus. When a spring is stretched, its wire's length doesn't change, but its shape does. This is why only the shear modulus of elasticity is involved in the stretching of a spring. {{citation needed|date=April 2021}}