Engineering Mechanics: Statics
Equilibrium of Rigid Bodies – 2D
• The necessary and sufficient condition for the static equilibrium of a
body are that the resultant force and couple from all external forces
form a system equivalent to zero,
• For a rigid body in static equilibrium, the external forces and
moments are balanced and will impart no translational or rotational
motion to the body.
4 - 1
(
)
∑ ∑
=
∑
×
=
=
00 FrMF
O
r
r
r
r
∑=
∑=
∑=
∑
=
∑
=
∑
=
000
0
0
0
zyx
zyx
MMM
F
F
F
• Resolving each force and moment into its rectangular components
leads to 6 scalar equations which also express the conditions for static
equilibrium,
