71. The algebraic sum of moments of the forces forming couple about any point in their plane is

A.Equal to the moment of the couple

B.Constant

C.Both of above are correct

D.Both of above are wrong

72. A single force and a couple acting in the same plane upon a rigid body

A.Balance each other

B.Cannot balance each other

C.Produce moment of a couple

D.Are equivalent

73. If three forces acting in one plane upon a rigid body, keep it in equilibrium, then they must either

A.Meet in a point

B.Be all parallel

C.At least two of them must meet

D.All the above are correct

74. The maximum frictional force which comes into play when a body just begins to slide over another surface is called

A.Limiting friction

B.Sliding friction

C.Rolling friction

D.Kinematic friction

75. The necessary condition for forces to be in equilibrium is that these should be

A.Coplanar

B.Meet at one point

C.Both (A) and (B) above

D.All be equal

76. If three forces acting in different planes can be represented by a triangle, these will be in

A.Non-equilibrium

B.Partial equilibrium

C.Full equilibrium

D.Unpredictable

77. If n = number of members and j = number of joints, then for a perfect frame, n =

A.J - 2

B.2j - 1

C.2j - 3

D.3j - 2

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