The shear modulus is also known as

Options

A. bulk modulus
B. Young's modulus
C. modulus of rigidity
D. Possion's ratio

Explanation

To determine what the shear modulus is also known as, we can analyze the options provided in the question. The shear modulus is a measure of how a material deforms under shear stress. Here’s a step-by-step breakdown of the options:

1. **Understanding Shear Modulus**:
- The shear modulus (often denoted as \( G \) or \( J \)) is defined as the ratio of shear stress to shear strain. It describes how a material deforms when subjected to shear forces.

2. **Evaluating the Options**:
- **Buck Modulus**: This is related to the bulk modulus, which describes how a material compresses under uniform pressure. It is not the same as shear modulus.
- **Young's Modulus**: This is a measure of tensile elasticity, which describes how a material stretches or compresses under axial loads. It is not related to shear.
- **Modulus of Rigidity**: This term is actually synonymous with the shear modulus. It describes the same property of materials under shear stress.
- **Poisson's Ratio**: This is a measure of the ratio of transverse strain to axial strain in a material. It is not related to shear modulus.

3. **Conclusion**:
- The correct answer is that the shear modulus is also known as the **modulus of rigidity**.

### Final Answer:
The shear modulus is also known as the **modulus of rigidity**.