Applied Mechanics and Graphic Statics
If a set of given forces are such that their free vectors build a closed polygon, then

The resultant force is zero but resultant couple is not zero
The resultant force is zero but resultant couple may not be zero
The resultant force and resultant couple are always zero
The resultant force and resultant couple both may not be zero

ANSWER DOWNLOAD EXAMIANS APP

Applied Mechanics and Graphic Statics
The following is in unstable equilibrium

A uniform solid cone resting on its base on a horizontal plane
A uniform solid cone resting on a generator on a smooth horizontal plane
A satellite encircling the earth
A solid cube resting on one edge

ANSWER DOWNLOAD EXAMIANS APP

Applied Mechanics and Graphic Statics
The following is not a law of static friction:

The force of friction always acts in a direction opposite to that in which the body tends to move
The force of friction is dependent upon the area of contact
The magnitude of the limiting friction bears a constant ratio to the normal reaction between two surfaces
The force of friction depends upon the roughness of the surface

ANSWER DOWNLOAD EXAMIANS APP