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. 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.

AdditionSubtractionTranslationRotation

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

∑Fy=0∑F≠0∑Fx=0∑Fz=0

3. Which of the following is valid if two forces are represented by two sides of a triangle in order?

The resultant of two forces is represented by the third side in reverse orderThe resultant’s magnitude is greatestThe resultant’s magnitude is zeroThe resultant of two forces is represented by the third side in the same sequence

4. Work done is best given by___________

dU = FdrdθdU = FdrcosθdU = FdrcotθdU = Fdrsinθ

5. We first make equilibrium equations of the body by considering all the three dimensional forces and then the free body diagram is made and solved. Thus the criteria for the potential energy equilibrium.

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

6. The net force of the body is zero that means the force are not being applied to the body at all and hence the body has achieved stability.

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

7. What is Engineering Mechanics?

Study of bodies under motion without considering forcesStudy of bodies only under restApplication of mechanics to issues involving common engineering aspectsStudy of bodies only under motion

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

Don't KnowFalseMaybeTrue

9. The moment is the cross product of which of the following two vectors/scalars?

Radius and Force scalarsForce and Radius scalarsForce and Radius vectorsRadius and Force vectors

10. The point of application where the total weight can be expected to be concentrated if the gravitational force is dispersed across the volume of the body is called ______

The centroid of the bodyMoment of inertiaCenter of gravity of the bodyThe surface of the body

11. Find the tension in the cable AC.

89N23.6N55N-29N

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

PerpendicularParallelNormalTangential

13. The moment of the resultant of two concurrent forces to a center in their plane is equal to

The algebraic sum of the moments of the components to a different centreThe difference in component moments with respect to a different centreThe difference between the components moments at the same centreThe algebraic sum of the moments of the components to the same centre

14. Work done by a spring to a body from moving it from x1 to x2 distance is given by _________

15. For the conditions of the equilibrium of the body, i.e. the rigid body only the external forces defines the equilibrium. And the support reactions only cancels out the rotation part of the body and thus the potential energy of the body is stored in it.

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

16. What is the the effect of a force upon a body according to the principle of transmissibility of forces?

Maximum when acting at the body’s centre of gravityMinimum when acting at the body’s centre of gravityDifferent at various locations along its line of actionThe same at all points along its line of action

17. The principle of work was proposed by________________

Mathematician Jean BernoulliChemist Jean BernoulliPhysios Jean BernoulliJohn Jean Bernoulli

18. 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 ray shown may be correct, but the body is not said to be in equilibriumThe diagram is wrongThe body is said to be in equilibrium only, as the other forces will cancel out that rotation

19. ∑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.

TrueDon't KnowFalseMaybe

20. We use sometimes the measures to know the direction of moment in the calculations of the moments caused by the gravitational forces over the body above the ground level. Which one is right about it(consider the mentioned axis to be positive)?

Thumb is z-axis, fingers curled from y-axis to x-axisThumb is z-axis, fingers curled from x-axis to y-axisThumb is y-axis, fingers curled from x-axis to z-axisThumb is x-axis, fingers curled from z-axis to y-axis

21. Which of the following doesn’t affect frictional force?

Reaction of surfaceForce tending cause motionSurface roughnessArea of contact

22. Which of the following is correct for the forces which are considered in the potential energy calculations?

The application of the conditions of the equilibrium of the body is valid throughoutThe application of the conditions of the equilibrium of the body is valid only if the forces are collinearThe application of the conditions of the equilibrium of the body is valid only if the forces are perpendicularThe application of the conditions of the equilibrium of the body is valid only if the forces are parallel

23. Which of the following conditions doesn’t affect the magnitude of the moment?

If the resultant is maximalIf the point of application of force is along the line of actionIf the point of application of force is opposing the line of actionIf the moment of centre is shifted along a line perpendicular to the line of action

24. Air also resist the body in the motion. The maximum value of the frictional force is called _________

Non-Limiting Action FrictionLimiting FrictionLimiting Action FrictionNon-Limiting Friction

25. If solving the question in 3D calculations is difficult, then use the 2D system and then equate the total net force to zero, thus the method for solving the work done.

Don't KnowFalseMaybeTrue