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Biomechanics
kinetics
24
Science
Undergraduate 4
04/03/2012

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Term
force
Definition

a push or pull acting on a body; vector quantities; measured in Newtons; 

 

point of application: where it makes contact

line of action: how you draw lever arms

Term
free body diagram
Definition
illustrates all of the external forces acting on an object
Term
examples of external forces
Definition

weight (gravity)

Ground Reaction Force

Friction

Fluid Resistance

Term
examples of internal forces
Definition

joint reaction force

muscle force

Term
Newton's First Law of Motion
Definition

Intertia: object's resistance to a change in motion; measured by an object's mass (kg)

tries to resist acceleration

more mass=more inertia

Term
Newton's Second Law of Motion
Definition

Accerleration: F=ma

must have an unbalanced force to have accerleration

sum cannot equal zero if you're going to overcome accereleration

Term
Newton's Third Law of Motion
Definition

Reaction: for every active force, there is a second force that is equal in magnitude, yet opposite in direction

forces ALWAYS occur in pairs

what we feel is the force coming back to us (like when punching a wall)

Term
Angular Analog of Inertia
Definition

mass moment of intertia: I=mk^2

centroid of where mass is; takes into consideration the shape of the axis, decreases k, less restance to spin, so will spin faster; 

moment of inertia, increase forgiveness of bat, club, etc

Term
Angular Analog of Acceleration
Definition

moment (M) or torque

rotational force

M=I(alpha)

Term
Angular Analog of Reaction
Definition

for every appled moment, there is a second moment that is equal in magnitude, yet opposite in direction

edge of a cliff...when falling backwards, rotate arms that direction to push you back forward

Term
moment
Definition

rotart effect of a force; angular equivalent of force; vector; rotational and twisting actions;

AKA: moment of force or torque

true definition of what happens inside the body

Term
moment vector
Definition

governed by right hand screw rule; 

1. curl fingers in direction of rotation

2. direction the thumb point represents direction of vector

magnitude given in Nm

sign based on coordinate system

Term
four basic functions of simple machines
Definition

1. balance two or more forces

2. change the directin of an applied force

3. mechanical advantage for Speed/ROM

4. mechanical advantage for force production

Term
First Class Lever
Definition

FAR

products must equal each other to be at equilibrium

length of lever arms allows for mechanical advantage

longer RMA=speed/ROM

longer FMA=force production

only class that can accomplish all four fxns

Term
first class lever examples
Definition

Triceps press down (elbow extension)

Neck extension

Term
Second Class Lever
Definition

ARF

FMA will always be longer than RMA

least common in body

major function: force production

Term
second class lever examples
Definition

calf raises

push ups

Term
Third Class Lever
Definition

AFR

most common in body

insertion/tendon is where force is

muscles set up lever systems, not bones

Term
third class lever examples
Definition

seated knee extension

elbow flexion (biceps curl)

Term
first class pulley
Definition

external surface that changes line of pull of a muscle

ex: patella-increases horizontal angle of pull

Term
second class pulley
Definition

trochlea is involved-internal surface that changes line of pull of a muscle

ex: lateral malleolus: 3 peroneus-eversion; longus/brevis: plantar flexion; tertiary: dorsiflexion

ex: eye-anteror lateral position; oblique superior

second and fifth equally most common

Term
third class pulley
Definition

joint structure itself causes a change in the line of pull

ex: knee-sartorius goes around knee to attach because of condyles

Term
fourth class pulley
Definition

as muscle contracts, it changes angle of joint, which changes its own line of pull

ex: forearm-pronators, suppinators; pronator teres

no stationary axis

Term
fifth class pulley
Definition

must be two muscles: deep and superficial

deep muscle shortens and increases cross-sectional are, which changes angle of pull of superifical muscle

ex: gastroc/soleus; biceps/brachialis

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