PTA 220: basic biomechanics chp.2

muskuloskeletal

major system producing human movement

biomechanics

principles and methods of mechanics and apply them to the structure and function of the human body creating movement and stability

mechanics

branch of physics associated with forces and the effects

statics

associated with non moving or nearly non moving systems

dynamics

associated with moving systems

kinetics

forces producing

kinematics

motion created by the created force (time, space, mass)

osteokinematics

manner in which bone moves in space

arthrokinematics

how adjoining joint surfaces move in relation to one another

scalar

quantity describes magnitude only, does not have a direction (speed, length, area, volume, mass)

mass

amount of matter in an object

vector

magnitude and direction (force, velocity, acceleration)

magnitude

amount of measurement

direction

direction in which magnitude is applied

force

amount and direction of push or pull action, creates compression and traction and can come from internal and external forces

gravity

attraction between earth and an object

gravitational force

exerted on a person as a result of gravity

weight

gravitational forces and mass

ground reaction

upward force from a supporting surface when an object pushes down on the surface

friction

between 2 surfaces increasing resistance to motion of one surface in relation to another

linear force

two or more forces acting along the same line

parallel force

occur in the same plane

force couple

two forces act in equal but opposite direction resulting in turning effect

concurrent force

two or more forces pushing or pulling in different directions

resultant force

sum of magnitude and direction of each individual force vector

traction

joint distraction

compression

joint approximation

shear

joint sliding

bending

when force is not applied at axis

torsional

twisting motion

torque (moment of force)

ability of force to produce rotation about an axis

amount of torque

amount of force exerted and the distance from the axis

increasing the force applied to the handle

increasing length of handle

torque can be increased by

moment arm

perpendicular distance between the muscle ,line of pull and the center of the joint

angle of application

angle at which force is applied

rotary

perpendicular to an object

angle of pull at 90 degrees

when is torque its greatest

angular force

the perpendicular distance between the joint axis and the line of pull is larger

stabilizing force

the perpendicular distance between the joint axis and the line of pull is very small

newtons law of inertia

an object at rest tends to stay at rest and an object in motion tends to stay in motion

newtons law of acceleration

the amount of acceleration depends on the strength of the force applied to an object

newtons law of action/ reaction

for every action there is an equal and opposite reaction

state of equilibrium

state of remaining fixed or steady against the force of gravity

center of mass (COM)

sum of mass of all body segments

center of gravity (COG)

point at which gravity acts on COM

base of support (BOS)

area between support surfaces

line of gravity (LOG)

imaginary vertical line passing through COG

levers

effort is applied at 1 point resistance applied at some other point with lever pivoting on a fulcrum/axis

force (effort) (f)

exact point where effort is applied cause the lever to move

resistance (load) (r)

load to be overcome or moved

axis (fulcrum) (A)

fixed point at which motion occurs

force arm (FA)

distance between the force and the axis, distance from insertion of the muscle to the joint (axis)

resistance arm (RA)

distance between the resistance and the axis

A= axis in the middle

type I lever

R= resistance in the middle

type II lever

F= force in the middle

type III lever

type I lever

best design for balance

type III lever

most common in the body

pulleys

to either change the direction of a force or to increase or decrease the magnitude of a force

fixed pulley

acts as a first class lever with the force on one side of the pulley (axis) and resistance on another

movable pulley

the resistance is suspended from the pulley, resistance is supported by both segments of the rope on either side of the pulley

inclined plane

flat surface the slants, exchanges increased distance for less effort