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81.

Coulomb friction is

A.	Friction between electrically charged bodies	B.	Friction between bodies having relative motion
C.	Friction between solids and liquids	D.	Friction between dry surfaces
E.	Friction between lubricated surface

82.

The maximum frictional force which comes into play when a body just begins to slide over the surface of another body is known as

A.	Dynamic friction	B.	Rolling friction
C.	Kinetic friction	D.	Limiting friction
E.	Sliding friction

83.

Which one of the following is not the law of dry friction?

A.	If friction is neglected, the reactions are always normal to the surfaces on contact	B.	Friction always acts to oppose the relative motion of the free body
C.	If static friction is acting, the value of the friction force may vary from zero to its maximum value	D.	The force of friction is always normal to the surface
E.	All of the above

84.

The angle of friction is

A.	The angle which frictional force makes with the normal	B.	The anle at which the force applied from external souce will cause movement
C.	The angle at which fictional force is inclined to external force	D.	The angle between the normal reaction and the resultant of normal reaction and the limiting friction
E.	None of the above

85.

Kinetic friction is

A.	Maximum value of frictional force when a body is about to move	B.	Friction between two well lubricated bodies
C.	Friction force acting when the body is in motion	D.	Driction force which keeps a body in motion
E.	None of the above

86.

The coefficient of friction is

A.	The angle between the normal reaction and the resultant of normal reaction and the limiting friction	B.	The tangent of the angle between the normal reaction and the resultant of the normal reaction and the limiting friction
C.	The tangent of the angle of the net resultant force with the direction of motion	D.	The tangent of the angle between the normal reaction and direction of limiting friction
E.	The tangent of the angle between the horizontal plane and the resultant force

87.

The limiting force of fiction is

A.	The value of friction force which stops the movement of the body	B.	The value of friction force which cannot exceed under a situation
C.	The friction force acting when the body is just about to move	D.	The friction force acting on a body when it is in motion
E.	Double of the normal friction

88.

If the angle of friction is zero a body will experience

A.	Infinite friction	B.	Zero friction
C.	The force of friction will act normal to the plane	D.	The force of friction will act in the direction of motion
E.	None of the above

89.

A couple consists of a force P acting at a point A whose coordinates are (-1,2,4) m and force - F acting at a point whose coordinates are (2,3, -2)m. If F = 3i + 2j - 4k in kg units the moment of the couple in kg - m units would be

A.	4i - 3j + k	B.	8i - 6j - 3k
C.	16i - 12j - 6k	D.	12i - 3j + k
E.	8i + 5j + 3k

90.

A rigid body is in equilibrium under the action of these forces when

A.	These forces are equal	B.	The lines of action of these forces are parallel
C.	The lines of action of these forces meet in a point	D.	(A) and (B) above
E.	(B) and (C) above