90°
30°
60°
45°

Applied Mechanics and Graphic Statics If two forces are in equilibrium, then the forces must (i) Be equal in magnitude (ii) Be opposite in sense (iii) Act along the same line

Only (i)
All (i), (ii) and (iii)
(i) and (ii)
(i) and (iii)

M’L-‘T*
M’L’r2
M’L2T2
M’L’T3

Applied Mechanics and Graphic Statics The Law of Polygon of Forces states that

If forces acting on a point can be represented in magnitude and direction by the sides of a polygon taken in order, then the resultant of the forces will be represented in magnitude and direction by t
If forces acting on a point can be represented in magnitude and direction by the sides of a polygon in order, the forces are in equilibrium
If a polygon representing the forces acting at point in a body is closed, the forces are in equilibrium
If forces acting on a point can be represented of a polygon taken in order, their sides of a polygon taken in order, their resultant will be represented in magnitude and direction by the closing side

Applied Mechanics and Graphic Statics A cube on a smooth horizontal surface

Cannot be in unstable equilibrium
Can be in any of these states
Cannot be in stable equilibrium
Cannot be in neutral equilibrium