1. Chapter 3 Equilibrium of Coplanar Force Systems
Statics
Chapter 3
Equilibrium of Coplanar Force Systems

2. Equilibrium Equations
Body is equilibrium when resultant of all external forces are zero
All forces
All moments
Sums of all corresponding rectangular components must be 0
External forces about an arbitrary point must be 0

3. Free Body Diagram
Is a sketch of a body isolated from its supports or other connected bodies with all external forces indicated
Should included clearly the magnitude direction and location of all external forces, including weight, applied forces, reactions and dimensions and angles
Weight – represents the gravitational attraction of the earth – acting downward through center of gravity
Applied forces – loads that are applied to the free body
Reactions – represents the constraining forces exerted or the free body by the supports or by the connected bodies
Dimensions and angles – must included all dimension and angles and location of all forces
Internal forces must not be included.

4. Types of Supports Roller supports with one unknown reaction element
Examples – page 105
Hinge support with two unknown reaction elements
Examples page 105
Fixed Support with three unknown reaction elements
Examples page 106
Pulley
Linear Spring
F=kx
Example 107
Example 3-1, 3-2, 3-3

5. Equilibrium of a concurrent coplanar force system
Body subjected to concurrent coplanar forces is in equilibrium if the resultant of the forces acting on the body is zero.
Moment of the forces about the common point is always zero
Equilibrium conditions would be Sum Fx=0 and sum Fy =0
Example 3-4 page 111
Example 3-5 page 112
Example 3-6 page 113
Example 3-7 page 114

6. Equilibrium of a non concurrent coplanar force system
Sum of Fx =0
Sum of Fy =0
Sum of M=0
If a problem contains to moments
Sum of Ma =0
Sum of Mb =0
X axis is arbitrarily and line segment AB must not be perpendicular to the x axis
Example 3-8
Example 3-9
Example 3-10
Example 3-11
Example 3-12