external forces

kinetics

• analysis of the forces

• produce, arrest, modifies motion

force

• push or pull that changes the motion of the object

• results to rotation motion

contact force

• direct contact between two objects

• applied forces, friction

long range forces

• forces that can act over distances

• gravity, EMF

displacement

vector that points an object from initial position to final position

equilibrium

no movement due to equal forces

1º source of force

• muscles

• gravity

• externally applied resistance

• friction

mass

amount of matter

weight

force of gravity acting on the object

moment

• result of force acting at a distance

• M = d x F

1st law of motion

law of inertia / equilibrium

• A body at rest will remain at rest unless otherwise an external force acted on it

2nd law of motion

law of acceleration / mass

• A change in the acceleration of a body occurs in the same direction as the force that caused it

• the acceleration of a body is proportionate to the magnitude of the net forces acting on it and inversely proportionate to the mass of the body

• EX. deadlift

3rd law of motion

law of action & reaction

• for every action there is an opposite & equal reaction

force system

identification of all forces acting on the object

linear force system

all forces are in the same line

parallel force system

two or more parallel forces acting at some distance from each other

center of gravity

• females have slightly higher COG than males

• adult: slightly ant to S2

• pregnant: anterior & superiorly

• infant: xiphoid process

to enhance equilibrium, maximize stability, & achieve balance

• lower COG

• > weight

• larger BOS

line of gravity / weight line

line from COM to the center of the earth

ground reaction force

• forces applied to the ground by the foot & vice versa

• 3rd law of motion

moment

• resultant force

• force application distant to the center of rotation

types of forces

• tension

• compression

• shear

• torsion

• bending

tension

• traction / distraction

• applied perpendicularly to the surface

compression

• approximation

• applied perpendicularly to the surface

• direction of force is towards one another

shear

• applied parallel to the surface

• - through moving one object along the surface of another

friction

parallel to contacting surface but opposite to the direction of shear

torsion

• rotation / twisting

• rotation of a segment around its long axis

bending

parallel forces applied to unsegmented object = equilibrium

translation / rotation

bending force is applied on unconstrained object