Kinetics and Forces Lecture Notes

Flashcards on Kinetics and Forces

Kinetics

Examines the forces that cause or influence movement and forces that allow maintenance of equilibrium or balance.

Force

The action of one body on another; a vector quantity with magnitude and direction.

Linear Force

Forces that create linear or translatory action, measured in Newtons (N).

Rotational/Angular Forces

Also known as 'moment' or 'torque,' represented by a curved arrow indicating direction, measured in Newton.meters (N.m).

Moment

The product of a linear force and a perpendicular distance from the linear force to an axis, generating potential for rotation.

External Forces

Forces exerted on the body from outside sources such as gravity, weights, and resistance.

Internal Forces

Forces usually in response to some external stimuli or external forces.

Tension/Tensile

Equal and opposite loads extending outward from the surface of a structure, applied parallel to the long axis of an object, lengthening and narrowing it.

Joint Distraction/Distractive

A force perpendicular to a joint surface, directed away from that joint surface, allowing for separation of the joint surfaces.

Compression/Compressive

Equal and opposite loads applied toward the surface of a structure.

Joint Compression/Compressive Forces

Applying perpendicular forces to joint surfaces directed toward the surface in an attempt to bring the surfaces together.

Shear

Any force (or component of a force) that has an action line parallel to contacting surfaces (or tangential to curved surfaces) that creates or limits movement between surfaces.

Bending

Load applied to a structure in a manner that causes it to bend about a pivot point, a combination of compression/tension.

Torsion

Load applied to a structure in a manner that causes it to twist about the structure’s long axis, creating shear stresses.

Combined Loading

Combination of more than one loading modes.

Mass

Amount of matter of which a body is composed.

Center of Mass (CoM)

Point at which a body’s mass is concentrated in equilibrium, also known as Center of Gravity (CG).

Gravity

A force that pulls a mass by earth’s mass causing object to accelerate toward the earth giving an object weight.

Weight

The product of mass and gravity (Weight = mass * g), making it a force and a vector quantity.

Line of Action

The line along which a force acts, representing the orientation of the force.

Point of Application

The location where the tip of the tail goes when a vector is drawn.

Line of Gravity (LoG)

Represents effect of gravity on the body, parallel to the trunk and extremities in anatomical position.

Base of Support (BOS)

Define by contact of system to ground – may include assistive devices or other objects.

Ground Reaction Force Vector (GRFv)

The force with the ground in turn results with the ground reacting or ‘pushing back’.

Stability

Ability to maintain or return to a steady state in presence of perturbations; assessed through CoM, LoG, and BoS.

Balance

Capability of a system to move without falling, the integration of systems whose ultimate goal is to maintain static or dynamic stability.

Internal Moment

Forces generated inside the body by tissues like muscles, tendons, and ligaments.

External Moment

Forces acting on the body from external sources like gravity or added resistance.

Moment Arm

Perpendicular distance from the line of action of a force to the axis of rotation; also called force arm, resistance arm, or effort arm.

Angle of Application

The angle between the line of action of the muscle and the long axis of the bone onto which the tendon inserts