Unit II Flashcards
If two forces are applied to an object simultaneously, the ______ vector is a combination of the two
resultant
Newton’s third law of motion: “equal & opposite force”
Force straight down results in GRF force straight up
Force against ground backwards and down causes force up and forward
Ground Reaction Forces
As we move away from earth’s surface, our weight (mass+gravity) diminishes but never full disappears
Ther is always some fraction of gravitational pull toward the Earth, even in outer space
Newton’s Universal Law of Gravitation
Gravity pulls us down causing an acceleration downward at
9.81m/s^2
What is the weight equation?
Fweight= mass x gravity
How much GRF do we need against gravity for us to not move?
enough to bring the net force to zero
____ is the tendency of an object to keep moving
momentum
What is the equation for momentum?
M= Mass x velocity
Two people can have similar momentum, even with different mass, provided that the person with less has more ______.
velocity
When two object collide, there is a transfer of ____ ____ from one object to another
linear momentum
What is an example of the conservation of linear momentum?
baseball impact with bat: after impact, bat loses velocity but ball gains it
Describes the amount of time that force is applied to an object
Impulse
____ is neccessary to change momentum
impulse
What is the equation for impulse?
Impulse= Force x Time
What is the equation for impulse in relation to momentum?
Impulse= the change in momentum
F x t= m x change in velocity
more time x more force = more impulse means more total change in ______
velocity
_____ is the rate at which you develop force
RFD
Higher RFD= ___ force generation
faster
Lower RFD= ____ force generation
slower
High RFD= ___ impulse
higher
Low porosity, 5-30% of bone volume is occupied by non-mineralized tissue
Cortical bone
high porosity, 30-90% of bone volume is occupied by nonmineralized tissue
Trabecular bone
The threshold stimulus that initiates new bone formation
Minimal Essential Strain
Goal is to maximize diameter of bone and _____ thickness
cortical
MES=
1/10th of the force required to fracture bone
Bone adaptation take about____ months to increase BMD
6
stronger forces of muscular contraction= more mechanical stress on bone= increase in bone____ and bone ____
mass, strength
Which principle to increase bone strength and muscle?
Progressive Overload
Which principle is important for BMD increases?
SAID
What are the structural exercises that direct the spine and hip?
Back Squat
Power clean
Deadlift
snatch
Push jerk
Shoulder press
specificity of _____ is important
loading
changing distribution and direction of ___ ___ present a stimulus for new bone formation
force vectors
Define stress
load or force per unit area
define strain
deformation that occurs at a point in a structure in response to an externally applied load
Cortical Bone can withstand greater ____ but it fracture at __% strain
stress, 2
Trabecular bone fractures at ___ % strain
7.5
Define isotropic
having a physical property that has the same value when measured in different directions
Define anisotropic
not having a physical property that has the same value when measured in different directions
Both types of bones are ______tropic
anisotropic
Tension
is stress stretching or pulling away
compression
stress pointed at each other
torsion
twisting or torque
shear
from the side and opposing ends
bending
force are the pointed the same way but there is a fulcrum
Why are bones shaped the way they are? (flared out at the ends and tapered in the middle)
Increase area of contact (reduces contact stress or pressure)
Reduces weight and moment inertia
Why are bones hollow?
Reduces Weight
Allow for protected site for marrow and other cellular development
Increases strength in bending (for a given amount of bone material)
what are example of reduced load on the body?
Bedridden patients
Immobilization
Sedentary people older adults
astronauts
Early bone loading and RT in childhood and young adulthood likely results
in higher peak BMD
RT starting in adulthood and continuing through a lifetime slows
BMD loss
RT in childhood and through a lifetime probably provides substantial protection against
osteoporosis in women and men
_____ is a measure of the amount of force applied over a particular distance
work
The object or athlete moves from one point to another
work
What is the equation for work?
Work=Force x distance
Increase in work due to distance results in an increase in _____
Impulse
Increase in work due to force results in an increase in ___
Impulse
What kind of work is associated with a concentric muscle action?
Positive
What kind of work is associated with eccentric muscle action?
negative
No mechanical work done means what muscle action?
isometric
What are the equations for power?
Power= work/time
Power= f x velocity
The ability of a person or object to do mechanical work is
energy
What are the 3 types of energy
Kinetic
Graviational Potential
Strain
what is the unit for energy
joules
What energy is due to the motion of an object
kinetic
What is equation for KE?
ke= 1/2 mass x velocity^2
What is the equation for momentum?
M= mv
The faster an object is moving, the more the momentum and the more ___ ___ it has
Kinetic Energy
it is a form of stored energy that results from the acceleration of gravity
Gravitational potential energy
What is the equation for GPE
GPE= mass x gravtiational accerlation (9.81 m/s^2) x height
Objects can store ____ energy if they have ability to restore themselves back to their original shape after being deformed
strain
How much resistance a person can exert against external forces in order to maintain there positioning
stability
____ is the ability to control the forces that make a person stable
balance
a person that has control of their stability can manipulate it in a controlled manner has
balance
Resistance against being moved in a particular direction
linear stability
more mass = more ____
stability
___ ____ is resistance against being tilted, tipped over, and upended or spun around
rotary stability
____ must be applied to cause an object to spin
torque
increase in size of ___ ___ ___ will increase stability
base of support
Vertical line that passes through an objects cent of gravity typically centralixed within the base of support to maintain stability
Line of gravity
____ the center of gravity to increase stability
lower
___ mass to increase stability
increase
____ base of support in direction of force being received or applied to increase stability. Allows you to apply force over a longer distance without losing balance
extend
What are the four ways to manipulate stability
Size of base of support
Line of gravity with base of support
Center of gravity
Mass
