Principle of Virtual Work topics include: Work, conservative forces, potential energy, equilibrium potential energy criterion and stability configurations. The principle of virtual work (PVW) states that the virtual work of the forces applied to a system is zero when the system is in equilibrium.  The PVW states that the stress, body force, and traction are in equilibrium if and only if the IVW equals the EVW for every virtual displacement field.  The PVW was originally used to examine systems of rigid structures. It is a powerful method for solving problems involving several connected... Show more

Principle of Virtual Work topics include: Work, conservative forces, potential energy, equilibrium potential energy criterion and stability configurations.

The principle of virtual work (PVW) states that the virtual work of the forces applied to a system is zero when the system is in equilibrium. 

The PVW states that the stress, body force, and traction are in equilibrium if and only if the IVW equals the EVW for every virtual displacement field. 
The PVW was originally used to examine systems of rigid structures. It is a powerful method for solving problems involving several connected rigid bodies. When the system is in equilibrium, virtual work is zero. This allows the calculation of the resulting forces when a system undergoes a virtual displacement. 

The PVW was also known as “the law of lever” and was used by the Greeks, medieval Arabs, and Latins.

The potential energy criterion for equilibrium states that for systems with multiple degrees of freedom, the partial derivative of potential energy with respect to each coordinate must be zero for equilibrium. 

The stability at the equilibrium configuration remains as long as its potential energy is minimum at that configuration.

A stable configuration is a state that is not subject to variation. It is also known as a state of minimum energy.

 

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Engineering Mechanics Practice Test: Principle of Virtual Work

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25 Questions

1. For stability of equilibrium configuration the net moment acting on the body by various forces is zero.

FalseTrueDon't KnowMaybe

2. For the conditions of the stability of equilibrium configuration of the body, i.e. the body only the external forces defines the equilibrium. Because the internal forces cancels out so not to be considered.

The first part of the statement is false and other part is trueThe first part of the statement is true and other part is true tooThe first part of the statement is false and other part is false tooThe first part of the statement is true and other part is false

3. Couple moment is also considered as one of the criteria for the equilibrium of the potential of the body. It should be zero sometimes. So a couple moment is developed when _______ of the attached member is prevented.

TranslationSubtractionRotationAddition

4. If any external conservative force also is applied on the distributed loading then?

The net load will not be formed as all the forces will be cancelledThe net force will act on the base of the loading horizontallyThe net force will not to be considered, there would be a net force of the distribution, rest will be the external forcesThe net force will act at the centroid of the structure only

5. Which of the following needs to zero for the perfect equilibrium for the calculation of the work?

∑F≠0, ∑M=0 and ∑θ = 0∑F=0, ∑M=0 and ∑θ≠0∑F=0, ∑M≠0 and ∑θ = 0∑F=0, ∑M=0 and ∑θ = 0

6. Which of the following needs to zero for the stability of equilibrium configuration?

∑F≠0, ∑M=0 and ∑θ = 0∑F=0, ∑M≠0 and ∑θ = 0∑F=0, ∑M=0 and ∑θ≠0∑F=0, ∑M=0 and ∑θ = 0

7. If the body is in stability of equilibrium configuration, but it having a rotational curled ray shown in the free body diagram then:

Such rotations can’t be shown in the fbds(free body diagrams)The body is said to be in equilibrium only, as the other forces will cancel out that rotationThe diagram is wrongThe ray shown may be correct, but the body is not said to be in equilibrium

8. If the supports which are supporting a body at a certain height are not properly aligned then the reaction forces developed are adequate to support the body.

Statement is true only in 3DStatement is true only in 2DStatement is false throughoutStatement is true only in 1D

9. Which of the following is the basic law for mechanics?

Parallelogram lawNewton’s law of viscosityHooke’s lawNewton’s laws of motion

10. The principle of work was proposed by________________

Physios Jean BernoulliMathematician Jean BernoulliJohn Jean BernoulliChemist Jean Bernoulli

11. The conservative frictional force always acts ____________ to the surface of the application of the friction.

PerpendicularTangentialNormalParallel

12. What is the sum of squares of the cosine angles made by the conservative force vector with the coordinate axis?

123½

13. If a block moves from a height h above the ground then the work done is given by_______

14. If the resolved force or the force which you get as the answer after solving the question is negative for the equilibrium of the potential energy, then what does this implies?

The force is in the reverse direction w.r.t the direction set in the free body diagramThe force is not in the reverse direction w.r.t the direction set in the free body diagramThe force is possible, but in the direction perpendicular to the resultant forceThe force component is not possible

15. Work done is best given by _____________

dU = F.drcotθdU = FdrsinθdU = F.drdU = Fxdrdθ

16. In the explanation of the theory of friction over which conservative forces were acted upon, the block used to have an assumption. That is the upper portion of the block is considered to be rigid.

Don't KnowMaybeFalseTrue

17. ∑Fx=0, ∑Fy=0 and ∑Fz=0 are vector equations for the three dimensions. They are satisfied when the body is achieved it state of equilibrium and the network done is zero.

Don't KnowFalseMaybeTrue

18. For the conditions of the equilibrium of the body, i.e. the rigid body only the external conservative forces defines the equilibrium. Because the internal conservative forces cancels out so not to be considered.

The first part of the statement is false and other part is trueThe first part of the statement is true and other part is true tooThe first part of the statement is false and other part is false tooThe first part of the statement is true and other part is false

19. What does Newton’s third law states for the work done?

The rate of change of momentum is equal to the force appliedFor every reaction there is an opposite reactionThe body is tend to be rotated if the force is applied tangentiallyThe body is rest until a force is applied

20. Which of the following is the SI unit of force?

Kg mKg m2Kg m2/sKg m/s2

21. ∑Fx=0, ∑Fy=0 and ∑Fz=0 are vector equations for the three dimensions. They are satisfied when the body is achieved its state of equilibrium, and then the work done is calculated.

TrueFalseDon't KnowMaybe

22. What is not the criteria for the equilibrium in potential energy free body diagram?

∑F≠0∑Fx=0∑Fy=0∑Fz=0

23. ____________ is the phenomena that resist the movement of the two surfaces in contact. This phenomenon is also having its scope in the work and the conservative nature of the force.

MotionFrictionCircular movementRotation

24. The coefficient of kinetic friction when a body is moving from a height above the ground level to a smaller height is ____________ than coefficient of static friction.

Significantly largerLargerSmallerHighly larger

25. Potential energy is stored in the body if some work is done on it. Work done is best given by:

dU = FdrcosθdU = FdrdθdU = FdrsinθdU = Fdrcotθ