• id: JME-08-N06
• title: Shear Modulus
• tags: shear-modulus, rigidity, tangential

Shear modulus (also called modulus of rigidity, $G$ or $\eta$) measures resistance to shape deformation: $G = \frac{\text{Shear stress}}{\text{Shear strain}} = \frac{F/A}{\theta}$ where $\theta$ is the angle of shear in radians. SI unit: Pa. It applies to solids only — fluids have zero shear modulus (they flow under shear stress). For most materials, $G < Y$ (typically $G \approx Y/2.5$ for metals). Shear modulus is crucial in torsion problems — a shaft's resistance to twisting is directly proportional to $G$.