Question

Is Young's modulus the same as stiffness?

Answer 1

Young's modulus $\left(E\right)$:

1. The ratio of tensile stress $\left(\sigma \right)$ to tensile strain $\left(\epsilon \right)$, known as the Young's modulus $\left(E\right)$, is a feature of the material that indicates how easily it can stretch and deform.
2. Strain is extension per unit length $\left(\epsilon =\frac{dl}{l}\right)$ and stress is the amount of force applied per unit area $\left(\sigma =\frac{F}{A}\right)$.

$E=\frac{\sigma }{\epsilon }=\frac{F/A}{dl/l}$

Stiffness: The extent to which an object resists deformation in response to an applied force.

Therefore,

1. It is well known that a component's stiffness depends on both its material and its geometry.
2. At the material level, it is known that a substance's stiffness depends on its Young's modulus (also known as the modulus of elasticity and abbreviated to $E$).

Hence, Young's modulus is the same as stiffness.