Bulk Modulus
The ratio of normal stress (pressure) to volumetric strain, indicating a material's resistance to change in volume.
What is Bulk Modulus?
The ratio of the applied normal stress to the resulting volumetric strain.
Key formula / rule: Bulk Modulus
Key points
- Define bulk modulus.
- Understand the relationship between pressure and volumetric strain.
- Interpret the significance of bulk modulus for different materials.
- Calculate bulk modulus given pressure and volume change.
Common exam trap
Forgetting the negative sign in the formula, leading to an incorrect sign for bulk modulus.
Definitions
- Term
Bulk Modulus
- Meaning
The ratio of the applied normal stress to the resulting volumetric strain.
- Term
Volumetric Strain
- Meaning
The fractional change in volume of a body, given by ΔV/V.
- Term
Compressibility
- Meaning
The reciprocal of the bulk modulus, indicating how easily a substance can be compressed.
Learning objectives
Define bulk modulus.
Understand the relationship between pressure and volumetric strain.
Interpret the significance of bulk modulus for different materials.
Calculate bulk modulus given pressure and volume change.
Formulae
- Name
Bulk Modulus
- Note
ΔP is the change in pressure, ΔV is the change in volume, and V is the original volume. The negative sign ensures K is positive.
- Expression
K = - \frac{\Δ P}{\Δ V / V}
Prerequisites
Stress and Strain
Types of Elastic Moduli (Young's Modulus, Shear Modulus)
Pressure
Common mistakes
Forgetting the negative sign in the formula, leading to an incorrect sign for bulk modulus.
Confusing bulk modulus with Young's modulus or shear modulus.
Incorrectly calculating volumetric strain.
Keywords
Bulk Modulus
Elasticity
Compressibility
Normal Stress
Volumetric Strain
Pressure
Material Properties
Practice preview
A liquid is compressed by applying a uniform pressure of 10^7 Pa. If its volume decreases by 0.1%, what is the Bulk Modulus of the liquid?…
medium
A substance has a Bulk Modulus of 2.2 x 10^9 N/m². What does this value indicate?…
easy
The SI unit of Bulk Modulus is the same as the SI unit of:…
easy