The virtual work principle states that ______.
Show Hint
- external virtual work is equal to internal virtual work
- there is equilibrium of external and internal forces
- virtual work is inversely proportional to virtual displacement
- the potential energy of the system is equal to its kinetic energy
The Correct Option is A
Solution and Explanation
This question checks the exact statement of the principle of virtual work, a basic tool for solving equilibrium problems in structural mechanics.
- external virtual work is equal to internal virtual work: This is the principle of virtual work itself: for a body in equilibrium, the work done by external forces through a small virtual displacement equals the work done by internal forces through the matching virtual deformation. This is correct.
- there is equilibrium of external and internal forces: Force equilibrium is a separate condition used while deriving the method, but it is not what the virtual work statement itself says, so this option is wrong.
- virtual work is inversely proportional to virtual displacement: Virtual work is not defined by any inverse relation; it is simply force multiplied by virtual displacement, so this option is wrong.
- the potential energy of the system is equal to its kinetic energy: This mixes up energy conservation in dynamics with virtual work, which deals with work during a virtual displacement, not energy equality, so this option is wrong.
The correct choice is (A): external virtual work equals internal virtual work for a body in equilibrium.
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