Applied Mechanics and Graphic Statics
The necessary condition of equilibrium of a body is:

Algebraic sum of vertical components of all the forces must be zero
All (A), (B) and (C)
Algebraic sum of the moments of the forces about a point must be zero
Algebraic sum of horizontal components of all the forces must be zero

ANSWER DOWNLOAD EXAMIANS APP

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

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 always acts in a direction opposite to that in which the body tends to move
The force of friction depends upon the roughness of the surface

ANSWER DOWNLOAD EXAMIANS APP