For perfectly rigid bodies, the elastic constants, Y, B and n are

• (A) Y = B = n = 0
• (B) Y = B = n = infinity
• (C) Y = 2B = 3n
• (D) Y = B = n = 0.5

In the context of perfectly rigid bodies, the elastic constants represent how materials respond to stress. For such bodies, they do not deform under applied forces, which leads to specific values for these constants.

Understanding Elastic Constants

The elastic constants are defined as follows:

• Y (Young's Modulus): Measures stiffness.
• B (Bulk Modulus): Measures resistance to uniform compression.
• n (Shear Modulus): Measures resistance to shear deformation.

Values for Perfectly Rigid Bodies

For perfectly rigid bodies, the deformation is zero regardless of the applied stress. Therefore, the values of the elastic constants are:

• Y = 0
• B = 0
• n = 0

This leads us to the correct answer: (A) Y = B = n = 0.