Kin Biomechanics Flashcards
Force
Push or pull action that can be represented as a vector
vector
quantity that has both magnitude and direction
push a wheelchair, one pushes it with a certain speed and certain direction
velocity
vector that describes speed and is measured in units such as f/s or m/h
scalar
quantity that measures only magnitude
like length, area, volume, and mass
mass
amount of matter that a body contains
inertia
property of matter that causes it to resist any change of its motion in either speed or direction
Is mass a measure of inertia?
yes, its a measure of its resistance to a change in motion
torque
tendency of force to produce rotation around an axis
friction
a force developed by two surfaces, which tends to prevent motion of one surface across another.
3 laws of Newton
Law of inertia
Law of acceleration
Law of action reaction
(iaa)
Law of inertia
an object at rest tends to stay at rest and an object in motion tends to stay in motion
Law of acceleration
the amount of acceleration depends on the strength of the force applied to an object
(how fast it go, depends on how hard it hit!)
Law of action reaction
for every action there is an equal and opposite reaction
Linear force
two of more forces are acting along the same line
parallel forces
occur in the same plane and in the same or opposite direction.
concurrent forces
two or more forces acting on common point but will be pushing or pulling in different directions
The overall effect of two different forces
The resultant force
The parallelogram method
Approach used to determine the resultant force
Force couple
a turning effect from two or more forces acting in different directions
scapula rotating from serratus ant., and the upper and lower traps
Moment of force
Torque, or angular force
the twisting forces ( moment of force, or torque ) of a wrench can be increased by
increasing the force applied to lever
increasing the length of the handle
Moment arm (torque arm)
perpendicular distance from a forces line of push/pull to the axis of rotation
process of stabilizing, dislocating, and greatest force
at 90 degrees - greatest force
nearing 0 degrees - stabilizing force
moving beyond 90-180 degrees - dislocating force
state of equilibrium
all torques acting on object are even and balanced
gravity
mutual attraction between an object and earth
COG
point at which all planes of body intersect, or balance point of an object at which torque on all sides is equal
BOS
part of a body that is in contact with the supporting surface
LOG
imaginary vertical line from the COG toward the center of earth
stable equilibrium
object is in a position where disturbing it would require its COG to be raised
unstable equilibrium
only a slight force is needed to disturb an object
neutral equilibrium
objects COG is neither raised nor lowered when it is disturbed.
Soccerball
lever
rigid and can rotate around a fixed point when a force is applied
axis, force, resistance
axis - the fixed point around which the lever rotates
force - effort that causes the lever to move
resistance - load that must be overcome
Force arm
the distance between the force and the axis
Resistance arm
the distance between the resistance and the axis
First class lever
F__________________R
A
second class lever
R F
_____________________
A
third class lever
F R
_____________________
A
