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Chpt 5: Biomechanics

Kinesiology/ Biomechanics

TermDefinition
mechanics the branch of physics dealing with the study of forces and the motion produced by their actions
biomechanics involves taking the principles and methods of mechanics and applying them to the structure and function of the human body
statics deals with the factors associated with nonmoving or nearly nonmoving systems
dynamics involves factors associated with moving systems and can be divided into kinetics and kinematics
kinetics deals with forces causing mvmt in a system
kinematics involves the time, space, and mass aspects of a moving system
osteokinematics deals with the manner in which bones move in space without regard to the mvmt of jt surfaces
arthrokinematics deals with the manner in which adjoining jt surfaces move in relation to each other
force any action or influence that moves an object
vector quantity having both magnitude and direction
mass refers to the amount of matter that a body contains
inertia the property of matter that causes it to resist any change of its motion in either speed or direction
torque tendency of force to produce rotation about an axis
friction force developed by two surfaces, which tends to prevent motion of one surface across another
velocity a vector that describes displacement and is measured in units such as ft/s or mi/hr
newtons first law of motion or law of inertia an object at rest tends to stay at rest, and an object in motion tends to stay in motion. a force is needed to overcome the inertia of an object and cause the object to move, stop, or change direction
newtons second law of motion of law of acceleration the amount of acceleration depends on the strength of the force applied to an object. acceleration can also deal with a change in direction. force I needed to change direction, and the change in direction of an object depends on the force applied to it
newtons second law with mass acceleration is inversely proportional to the mass of an object. the same amount of force applied to two objects of differing mass, the object with the greater mass will accelerate less
newtons third law of action reaction for every action there is an equal and opposite reaction. the strength of the reaction is always equal to the strength of the action, and it occurs in the opposite direction
internal force such as a muscular contraction, ligamentous restraint or boney support
external force gravity, or any other externally applied resistance such as weight and friction
scalar quantity describes only magnitude. common terms are length, area, volume and weight
vector quantity describes both magnitude and direction
characteristics of force magnitude, direction, and point of application
linear force results when two or more forces are acting along the same line or plane
parallel forces occur in the same plane and direction with a counter force in the middle but in the opposite direction
concurrent forces two or more forces act in a common point but pull in different (divergent) directions
resultant force the net effect of these two divergent forces, and it lies somewhere in between
force couple occurs when two forces act in an equal but opposite direction resulting in a turning effect
torque or moment of force ability of force to produce rotation about an axis, rotary force
torque is also the amount of force needed by a muscle contraction to cause rotary joint motion
torque about any axis equals the product of the force magnitude and its perpendicular distance from the axis of rotation to the line of force
moment or torque arm perpendicular distance
torque has greatest when the angle of pull is at 90 degrees, and decreases as the angle of pull either increases or decreases from that perpendicular position
stabilizing force force generated by the mm. nearly all of the face generated by the mm is directed back into the jt, pulling the two bones together
angular force the force regenerated by the mm, in that the force generated by the mm is directed at the mvmt joint
dislocating force past 90 degrees, the stabilizing force is directed away from the joint
state of equilibrium when an object is balances, and all forces on it are even
gravity mutual attraction between the earth and an object
gravitational force always directed vertically downward toward the center of the earth
center of gravity (COG) balance point of an object at which weight on all sides is equal, it is also the point at which the planes of the body intersect
base of support (BOS) the part of a body that is ion contact with the supporting surface
line of gravity (LOG) imaginary vertical line passing through the COG toward the center of the earth
stabile equilibrium an object is in a position that to disturb it would require its COG to be raised
unstable equilibrium occurs when only a slight force is needed to disturb an object
neutral equilibrium when a objects COG is neither raised or lowered when it is disturbed
the lower the COG.. the more stable the object
stability increases... as the BOS is widened in the direction of the force
four simple machines used in engineering to change magnitude or direction of force levers, pulleys, wheel and axles, and incline planes
with machine is not found in the human body inclined plane
a lever is rigid bar that can rotate about a fixed point when a force is applied to overcome resistance
fixed point a lever rotates is the axis and sometimes referred to as a fulcrum
in the human body the force (F)... is what causes the lever to move and is usually muscular
resistance (R) that must be overcome for the motion to occur can include the weight of the part being moved, gravity, or an external weight
force arm (FA) is the distance between the force and the axis.
resistance arm (RA) is the distance between the resistance and the axis.
first class lever axis is located between the force and the resistance. designed for balance
second class lever axis at one end, resistance in the middle, and the force at the other end. used for power
third class lever has the axis at one end with the force in the middle and resistance at the opposite end. used for ROM, most common in the body
mechanical advantage the ratio between the force arm and the resistance arm
mechanical adv of a lever is determined by dividing the length of the force arm by the length of resistance arm (MA= FA/RA)
the greater the mechanical adv.. the less force is needed to cause motion
formula for when the FA is greater than the RA, as with a second class lever, the MA is greater than one MA= 2/1 MA=2
pulley consists of a grooved wheel that turns on an axel with a rope or cable riding in the groove. purpose is to either change the direction of a force, or to increase or decrease the magnitude of a force
fixed pulley simple pulley attached to a beam, acts as a first class lever with F on one side of the pulley (axis) and R on the other. used only to change direction
moveable pulley has one end of the rope attached to a beam then runs through the pulley to the other end where the force is applied. the load (resistance) is suspended from the moveable pulley
a single moveable pulley acts.. as a second class lever and increases the force of one of the levers (effort)
wheel and axel less common type of simple machine found in body, disguised as a lever. consists of a wheel or crank, attached to and turning together with an axel. typically used to increase the force exerted
calculation of the MA of a wheel and axel MA= radius of wheel/ radius of axle
inclined plane flat surface that slants. no examples of them in the human body. exchanged increased distance for less effort
the basic rule of simple machines what is gained in force is lost in distance, and vice versa
Created by: graykm
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