Strength of Materials
In the equation of virtual work, following force is neglected

All of the listed here
reaction of any smooth surface with which the body is in contact
reaction at a point or an axis, fixed in space, around which a body is con-strained to turn
reaction of a rough surface of a body which rolls on it without slipping

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Strength of Materials
Center of percussion is

the point of C.G.
the point of metacentre
the point of application of the resultant of all the forces tending to cause a body to rotate about a certain axis
point of suspension

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