Young's, Bulk and Rigidity Moduli
Y = longitudinal stress/longitudinal strain, B = -P/(DV/V) and G = shear stress/shear strain.
What is Young's, Bulk and Rigidity Moduli?
Y = longitudinal stress/longitudinal strain, B = -P/(DV/V) and G = shear stress/shear strain.
Key formula / rule: Y for stretching, B for volume change, G for shear.
Key points
- Compute elongation and stored energy in a stretched wire.
- Classify a deformation and select the appropriate modulus.
Common exam trap
Using Young's modulus for a volumetric compression problem.
Definitions
- Term
Young's, Bulk and Rigidity Moduli
- Meaning
Y = longitudinal stress/longitudinal strain, B = -P/(DV/V) and G = shear stress/shear strain.
- Term
Young's, Bulk and Rigidity Moduli — explanation
- Meaning
Each modulus describes resistance to a different kind of deformation, and elastic potential energy per unit volume equals half the product of stress and strain.
Learning objectives
Compute elongation and stored energy in a stretched wire.
Classify a deformation and select the appropriate modulus.
Formulae
- Key point
Y for stretching, B for volume change, G for shear.
- Key point
Compressibility is the reciprocal of the bulk modulus.
- Key point
Energy density = stress x strain / 2.
Prerequisites
PHY-U3-MPM-T1-S1-C1
Common mistakes
Using Young's modulus for a volumetric compression problem.
Forgetting the negative sign in the definition of the bulk modulus.
Keywords
Young
Rigidity
Moduli
Practice preview
A material is highly incompressible. Which of its elastic moduli will have a very high value?…
medium
The Rigidity Modulus (G) is also known as the:…
easy
For a perfectly rigid body, what would be the value of its Young's Modulus (Y)?…
hard