Exam 2 - Completed by Anna at 6:45 PM Flashcards
What is the definition of center of gravity?
The point of application of force due to gravity
____ and _____ are concentrated at the center of gravity
weight and mass
What is the point where all forces appear to act?
Center of gravity
For an object to be in equilibrium, the sum of the torques around the body need to be _____
0
What is the definition of line of gravity?
Line of application of gravity force
Center of gravity of the body is the sum of what?
segment center of gravities
Location of center of gravity of a human in normal standing position varies with what?
body build, age, and sex
Female center of gravity is what?
55% of standing height
Male center of gravity is what?
57% of standing height
Why do women have a lower COG?
wider hips/pelvis
COG is usually at which vertebrae?
Second sacral vertabrae
COG of a combined segment is about ______ _____ COG of individual segments
halfway between
COG helps facilitate ______.
motion
COG alters _____ ____
exercise loads
What are the 4 reasons to have a knowledge of COG?
Help facilitate motion, alter exercise loads, balance segments, and prevent falls
When segments change position, so does what?
COG of body
COG rises when what?
When you raise the height of your body
When walking, the body has a _____ COG and ______ equilibrium
High
Unstable
When walking what can cause displacement of the body?
small forces
Walking is what?
a sequence of disturbing and catching COG
People _____ COG for protection when there is uncertainty in control and balance
lower
Uncertainty in control and balance may require what?
more energy
Objects at rest = ?
equilibrium
At equilibrium, force and torque = ?
0
All objects at rest are _________
not equally stable
When an object in stable equilibrium is disturbed, what happens?
It moves, but the COG will return to its initial position
What are some examples of objects in stable equilibrium?
weebles, rocking chair
What happens in unstable equilibrium?
COG is disturbed and finds new position
The new position of COG when an unstable object moves is what?
lower
What happens when an object is in neutral equilibrium?
COG does not fall or return to initial position
What is an example of a neutral object?
A ball
What are 4 factors affecting stability?
- Size and shape of base of support
- Height of COG above base of support
- Location of LOG within base of support
- Weight or mass of body
Which LOG location would have best stability?
central to base of support
The center of gravity in the base of support is more stable with a _____ base
larger
When in a staggered position, the COG has resistance to which forces?
AP forces
When feet are spread shoulder-width apart, COG has resistance to which forces?
lateral forces
Squatting position has more _______ ______
Lateral stability
More angular displacement can occur before COG goes ____ _____
beyond BOS
When LOG is within BOS, this = ?
equilibrium
Mass of body is only a factor when what?
when motion or an external force is involved
The greated the mass of the body, the _____ the stability
greater
what is mobility’s relationship with stability?
inverse
What is the critical point?
change of state
What are important factors in mobility?
COG, LOG, BOS
What is force?
Entity which produces, halts, or changes direction of motion
How does force function?
Push or pull through contact or gravity
Force alters what?
the motion of body parts
Force = ?
mass*acceleration
W=?
mass * gravity
Weight is a force caused by what?
pull of gravity
What is load?
weight of an external object
What is strength?
the ability to lift or move weight
P=?
Force / Area
Force is a _____ ______
vector quantity
What are the aspects of force?
magnitude, point of application, line of application, direction
For a weight lifter to lift a 250 N barbell, what must they do?
apply a force greater than 250 N, in an upward direction, through the center of gravity of the barbell
What is newton’s first law?
An object at rest remains at rest, object in motion remains in motion, unless acted on by a force
The acceleration of an object is directly proportional to what?
The force causing it and inversely proportional to the mass of the object
Heavier objects wil have a ______ acceleration
lower
What is newton’s third law?
For every action force there is an equal and opposite reaction force
Injuries occur when you have what?
unequal forces
Pulleys are ____ or ____ systems
linear, concurrent
Pulleys can be in _____ or ____ positions
fixed, movable
What do pulleys do?
change the direction of force
What do single fixed pulleys do?
changes the line of action of force
single fixed pulleys have what mechanical advantage?
None
What is an example of a single fixed pulley?
cervical traction pulley
How do anatomical pulleys work?
Tendons deflected from straight course by bony prominences or soft tissue
What do anatomical pulleys do?
changes the angle of pull of muscle providing the force
Increase in angle of pull, increases what?
rotary component
When there is more force in the rotary component, there is more force in the ______ ______
osteokinematic motion
What are levers?
Rigid bars that can rotate about a fixed point when a force is applied to overcome a resistance
What are levers used to do?
- Overcome a resistance larger than the magnitude of the effort applied
- Increase the speed and range of motion through with a resistance can be moved
What are the 3 forces of levers?
axis/pivot, weight/resistance, moving/holding force
What are the moment arms of a lever?
effort arm, weight arm
What is the effort arm?
distance from pivot to force
What is the weight arm?
distance from pivot to weight
What is mechanical advantage?
Ratio between length of force arm and length of weight arm
MA=?
Force arm/ weight arm = Weight/ Force
A first class lever has what type of advantage?
force or distance
Where is the pivot on a first class lever?
Between the weight and force
A second class lever has what type of advantage?
force advantage
Where is the weight in a second class lever?
between the pivot and force
What is an example of a second class anatomical lever
hips
What kind of advantage does a 3rd class lever have?
distance advantage
Where is the force in a 3rd class lever?
between the pivot and weight
Which type of lever is the most prevalent in the body?
3rd class lever
In a 3rd class lever, how much force must you apply?
twice the force of the weight
When MA > 1, what type of advantage does the lever have?
force advantage
When MA < 1, what type of advantage does the lever have?
distance advantage
What is torque?
When a force is properly exerted on a rigid body pivoted about some axis, the body will tend to rotate about that axis
Torque is the tendency of what?
of a force to rotate a body about an axis
t = ?
r F sin f
d (moment arm) = ?
r sin f
Perpendicular distance from _____ to line of action of force
axis
clockwise torque =?
negative torque
counterclockwise torque = ?
positive torque
Torque in the arm is most when the resistance arm is where?
at 90 degrees from the LOG
Muscle forces that exert torque are dependent on what?
point of insertion of the muscle and length, tension, and angle of pull changes
What is Kinesiology?
the science dedicated to broad area of human movement
What are the subjects that are related to kinesiology?
sport psychology, motor learning, exercise physiology, biomechanics
Kinesiology is more ______ than biomechanics
qualitative
What is biomechanics
The application of principles and techniques of mechanics to structure, functions, and capabilities of living organisms
What subjects is biomechanics related to?
physics, chemistry, mathematics, physiology, and anatomy
Biomechanics is more _____ than kinesiology
quantitative
What is the purpose of the biomechanics of human movement?
describes, analyzes, and assesses human movement
biomechanics analyzes what?
a variety of movements, what is the same about them, and what changes
What is the definition of mechanics?
study of forces and their effects
What is the application of mechanical princlples to human and animal bodies in movement and at rest?
biomechanics
What are the 2 conditions of mechanics?
statics and dynamics
What are statics?
things that are not moving. Humans that are at-rest or moving with constant velocity. No acceleration. “Uniform Motion”
What are dynamics?
movement with acceleration/deceleration
What are the 2 areas of study in mechanics?
Kinematics and kinetics
What are kinematics?
the study of the effects/description of motion. displacement/velocity
What are kinetics?
The cause of motion. Deals with moving objects, and the forces that act to produce those motions
What are the 3 kinds of motion?
Linear, angular, and general
What is linear motion also known as?
translation
What is angular motion also known as?
rotary, rotation
What is general motion?
a combination of linear and angular motion
What limits the movement at the joints?
shape and fit
In linear motion, the ______ as a _____ is moved from one point to another
body as a whole
Any point on the object in linear motion can be used as a ______
reference point
In general, when an object is moving in linear motion, the parts ____________________________________
do not move relative to one another
What are the two types of linear motion?
rectilinear and curvilinear
What is rectilinear motion?
straight-line progression of the object
What is curvilinear motion?
Point on an object or body that moves in a linear fashion, but moved in a curved line
Objects moving in angular motion move around a _______
relatively fixed point
All points, regardless of how far they are from the pivot will what?
go through the same angle
Most of our joints go through what kind of motion?
general
Most projectiles move through what kind of motion?
general
What are the factors that determine linear motion?
The object is free to move
uniform force against the side of the object
force is direct to COG
Motion occurs unless there is resistance
What are the factors that determine angular motion?
Some portion fixed in place
Fulcrum or axis of rotation
force is applied to portion of the object that is free to move
What are biomechanics measured in?
metric system and english gravitational system
What is velocity measured in?
M/Sec^2
What is mass measured in?
slugs
What is force measured in?
lbs
What does linear kinematics measure?
distance and displacement
speed and velocity
acceleration
What is displacement?
change in position of an object
What must you know to measure displacement?
initial and final coordinates
Displacement is independent of a path if what?
end points are fixed
What is velocity?
the ratio of an object’s displacement and time interval
Speed is the ______, velocity includes _____
number
direction
What is average acceleration?
the ratio of change in velocity and time interval
Average acceleration is also said to be the rate at which you are what?
increasing or decreasing your speed
Different parts of the body have different ____ and _____
velocities and accelerations
velocity and acceleration depends on what?
how far the point is from the axis
Points near the axis have a displacement of _____ than those farther away
less
A point closer to the pivot has a smaller ______ ______
linear velocity
The furster a point is from the pivot point, the ______ its linear variables will be.
larger
