Statics Professor: Dr. Miguel Alonso Jr.

Outline Introduction Forces Moments Resultants Equilibrium

Introduction Statics is concerned with the equilibrium of bodies subjected to force systems Forces and Moments

Forces A force is the manifestation of the action of one body upon another Can arise from the direct action of two bodies in contact with one another You pushing on the wall Or from the “action at a distance” of one body upon another Gravity Magnetism

Forces can be either body forces or surface forces Mathematically, forces are represented as vectors A directed line segment having a tail and a head Defined by a magnitude and direction

Moments In addition to the pushing, or pulling effect on the point at which it acts, a force creates a moment about axes passing through the body Moments can be thought of as a tendency to rotate the body upon which it acts around a certain axis Computed as the cross product between the component of the force perpendicular to the axis and the distance from the component to the axis

Resultant Force Resultant force of a system is the equivalent force of the total system. It is the vector sum of the individual forces. Example 18.1 and 18.2

Equilibrium Any body is in equilibrium ( that is there is 0 movement) when the resultant force on the body is absolutely zero Vector sum of all forces is zero Resultant moment of the forces about each of the axes is zero

If all of the forces act in only one plane, (lets say the x-y plane), then equilibrium is met by Free body diagrams help in solving these types of problems An FBD is a neat sketch of the body showing all forces and moments acting on the body with all important linear and angular dimensions

Example 18.3 and 18.4

Practice Problems Chapter