TABLE OF CONTENTS Statics. That branch of mechanics which deals with the equilibrium of forces on bodies at rest (or moving at a uniform velocity in a straight line).
Force. The action of one body on another. It is a vector quantity defined by its magnitude, direction, and point of application ( P) (Fig. 5.1). The forces by which the individual particles of a body act on each other are internal. All other forces are external. The forces exerted by the body on its supports are called reactions. They are equal in magnitude and opposite in direction to the forces, called supporting forces, with which the supports act on the body.
Gravitation. The force of the earth's attraction directed toward the earth's center.
Moment The moment of a force F about a point O (Fig. 5.7) is
where l = perpendicular distance (called level arm l) from point O to the line of action of force F. This moment has the dimension of force length and is considered positive when tending to produce counterclockwise rotation around point O.
Free-Body Diagram. A structure or a part of a structure which is considered to be separated from everything else and mode "free." When a free body is diagrammed, vector arrows are placed representing the forces which the other parts exert upon the free body. The forces which the free body exerts upon...
