Question

According to the principle of virtual work, If the system of rigid bodies is in equilibrium under the action of a set of forces, then the work done by those forces during a small virtual displacement of the system must be equal to
1. Infinite
2. Zero
3. Unity
4. A non-zero constant
5. always changing

Answer 1

Correct Answer - Option 2 : Zero

Explanation:

Principle of virtual work

Case-1: For deformable or elastic bodies

• The total virtual work done is equal to zero.
• W_e + W_i = 0
• Where, W_e = External virtual work done and W_i = Internal virtual work done
• The internal virtual work done (W_i) by internal resistance (such as stress) is negative, hence \(\left| {{W_e}} \right| = \left| {{W_i}} \right|\)

Case-1: For rigid bodies

• In rigid bodies, there is no internal deformation. Hence, the internal virtual work done is always zero. Therefore external virtual work done is also zero.