A quantity possessing both magnitude and direction, represented by an arrow whose length is proportional to the magnitude and whose orientation in space represents the direction

A line of indefinite length of which a force vector is a segment

Two or more concurrent forces into which a single force may be resolved and having a net effect on a rigid body equivalent to that of the initial force

The point at which the axis of a moment intersects the plane of the forces causing the moment

The perpendicular distance from the line of action of a force to the point or line about which a moment occurs. Also called force arm.

The tendency of a force to produce rotation of a body about a point or line, equal in magnitude to the product of the force and the moment arm and acting in a clockwise or counterclockwise direction

A force system of two equal, parallel forces acting in opposite directions and tending to produce rotation but not translation

Equal in magnitude to the product of one of the fores and the perpendicular distance between the two forces

Non-concurrent forces having parallel lines of action

Forces having lines of action that do not intersect at a common point, the vector sum of which is a single force that would cause the same translation and rotation of a body as the set of original forces

Concurrent forces having the same line of action, the vector sum of which is the algebraic sum of the magnitudes of the forces, acting along the same line of action

Forces that operate in a single plane

Forces having lines of action intersecting at a common point, the vector sum of which can be found by applying the parallelogram law

The proposition that the vector sum of two concurrent forces can be described by the diagonal of a parallelogram having adjacent sides that represent the two force vectors being added

A single vector equivalent to and producing the same effect on a body as the application of two or more given vectors. Also called resultant.

A graphic technique for finding the vector sum of two concurrent forces by displacing one force vector parallel to itself until its tail coincides with the head of the other and completing the triangle with a vector that represents the resultant force

A graphic technique for finding the vector sum of a coplanar system of several concurrent forces by drawing to scale each force vector in succession, with the tail of each at the head of the one preceding it, and completing the polygon with a vector that represents the resultant force, extending from the tail of the first to the head of the last vector

The point at which the entire weight of a body may be concentrated so that, if supported at this point, the body would remain in equilibrium in any position

The point at which the entire weight of a body may be considered concentrated such that the moment about any line through the point is zero

The center of a one- or two-dimensional figure, about which the sum of the displacements of all points in the figure is zero

The uniform motion of a body in a straight line, without rotation or angular displacement

The circular motion of a body about an axis

A rigid element that pivots about a fulcrum to exert a pressure or sustain a weight at a second point by a force applied at a third

The point or support about which a lever turns

The ratio of output force to the input force applied to a mechanism

A graphic representation of the complete system of applied and reactive forces acting on a body or an isolated part of a structure

The branch of physics that deals with the effects of forces on bodies or material systems, comprised of statics and dynamics

The branch of mechanics that deals with the relations of forces producing equilibrium among bodies or material systems

The branch of mechanics that deals with the motion and equilibrium of bodies or material systems under the action of forces

The physical law that a body remains at rest or in motion with a constant velocity unless an external force acts on the body

Law of inertia

Having the same translational and rotational effect on a body

The tendency of a body at rest to remain at rest or of a body in motion to retain its velocity along a straight line unless acted upon by an external force

The force required to bring a set of concurrent forces into equilibrium, equal in magnitude but opposite in direction to the resultant of the concurrent force system and acting along the same line of action

A state of balance or rest resulting from the equal action of opposing forces

The physical law that the sum of the forces acting on a body is equal to the product of the mass of the body and the acceleration produced by the force, with motion in the direction of the resultant of the forces

The physical law that for every force acting on a body, the body exerts a force having equal magnitude and the opposite direction along the same line of action as the original force

Law of action and reaction

An external force acting directly on a body

An external force generated by the action of one body on another