Exam 2 Flashcards
definition: forces that cause motion or are caused by motion
linear kinetics
example of linear kinetics
gravity, impact force,
Newtons laws: the basis of ______
mechanics
What is newtons first law of motion
the law of inertia: the body in motion stays in motion or at rest stays at rest unless acted on by an outside force
definition: the quantity of motion a body possesses (body must be moving)
momentum
what is the equation for momentum?
M = m x v
how does momentum change?
by changing mass or velocity
in absence of _____ ______, the total momentum of a given system remains constant
external forces
definition: objects in a head on collision bounce off each other. combined momentum is conserved
elastic collision
definition: objects in the collision stay together after the collision and move together with the same velocity. combined momentum is also conserved
inelastic (plastic) collision
what is Newtons second law?
law of acceleration: force applied to a body causes acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body’s mass
what is the equation for newtons 2nd law of motion
F = m x a force = mass x acceleration
impulse is the product of _____ times ____
force times time
if an impulse acts on a system, it will change the ______ _____ of the system.
total momentum
landing in a relaxed rather than rigid manner allows reduction in ___ ____ on the joints by dissipating _____ over a long period of time.
impact forces; force
in impulse equations, what must mass be in ?
Kg
what is newtons third law?
law of action-reaction: for every action there is an equal and opposite reaction
what is an example of newtons 3rd law?
ground reaction force
when one body exerts a force on a second, the second body exerts a _____ force that is _____ in magnitude and _____ in direction to the first body
reaction; equal; opposite
What is a common force we can use to our advantage?
Ground reaction force
Jumpers use ground reaction force to convert ______ velocity to ______ velocity
horizontal to vertical
runners can experience _____ due to GRF
injuries
GRF & ______ data can determine the amount of _____ at each joint
kinematic; force
when running, each time your foot hits the ground, ____ x your body weight is exerted through your lower extremity
2 - 3 x
force pattern varies with running _____
style
GRF can be measured by a
force palate (precise scale that measures forces in 3 dimensions – x,y,z)
4 factors influencing GRF
- running speed 2. footwear 3. ground surface 4. grade of surface
(Newtons Law of ______) All bodies are attracted to one another with a force _______ to the product of their masses and _____ to the distance between them.
gravitation; proportional; inversely
definition: collision of two bodies in a small amount of time
impact
3 types of impact
- perfectly elastic 2. perfectly plastic 3. somewhere in between
what type of impact: the velocities of the 2 bodies remain equal before and after impact. example?
perfectly elastic. ball bouncing
what type of impact: at least one body deforms and does not regain its original shape and bodies do not separate. Example?
perfectly plastic. car crash
definition: a unit-less number between 0 and 1 that is used to describe the relative elasticity of an impact
coefficient of restitution
what does the number 1 represent ? the number 0 ?
1 = perfectly elastic 0 = perfectly plastic
when two bodies undergo a direct ______, the difference in their velocities immediately after an impact is _____ to the difference in their velocities immediately before impact.
collision; proportional
what does Hb stand for? Hd?
Hb = bounce height Hd = drop height
What unit does the coefficient of restitution use?
none. it’s a unit less number
work is the produce of _____ and _______ (distance)
force and displacement
what is the equation for work?
U = fd
definition: the object is moved in the same direction of the force
positive work
definition: the object is moved in the opposite direction of the force
negative work
what type of work do eccentric and concentric muscle contractions do?
concentric = positive work eccentric = negative
definition: rate of mechanical work
power
what unit is used to represent power?
watt
capacity of a body to do work
mechanical energy
3 types of mechanical energy
- kinetic 2. potential 3. strain
energy in motion
kinetic energy
energy due to position
potential energy
KE = ?
1/2 mv squared
PE = ?
weight x height OR mass x height x gravity
energy of elasticity stored energy in the deformation of an object
strain energy
example of strain energy?
pole vault pole, tendons
Strain energy (SE) = ?
1/2 kx squared k = stiffness, x = length
when gravity is the only acting external force, a body’s mechanical energy remains ______
constant (law of conservation of energy)
the work of a force is equal to the change in energy that it produces in the object acted on it
principle of work and energy
what is the equation for conservation of energy?
1/2mv squared = mgh (KE equation = PE equation)
torque is a moment of _____
force
torque is a _____ effect created by an applied force
rotary
torque is the ______ equivalent of linear force
angular
what is the equation for torque with a 90 degree angle?
T = F x r
a force applied through a body’s ______ of rotation results in linear motion or no motion depending on the _____ of force applied
center; amount
greater torque results in a greater tendency for _____ to occur and a greater angular _______
rotation; acceleration
definition: perpendicular and shortest distance between a force’s line of action and axis of rotation
moment arm
any deviation from the _______ will change the moment arm length
perpendicular
definition: pair of equal and opposite forces that produce torque in the same direction
force couple
in a force couple, both have equal ______, and even though they’re on opposite sides of the axis of rotation, their effects on the body are _____ together
magnitude, added
counterclockwise rotation is ______; clockwise rotation is _______
positive; negative
when examining the direction of joint rotation, what two things are important?
- position of the body 2. position of the person observing the movement (could be clockwise or counterclockwise depending on stance)
Joint torques produce movement of _____ _____
body segments
Muscles (through ____) pull on points across a center of rotation (_____), thus creating _______
tendons, joints, torques
agonistic and antagonistic muscles are working so the change in joint position is a result of ____ _____
net torque (whichever is greater produces net torque)
what 5 things are joint torques influenced by ?
- segment weight 2. segment motion 3. segment length 4. external motion 5. external forces (weight, pulley system, etc.)
what is the equation for torque when the angle is other than 90 degrees?
Fc = rF x sin0
_____ torques can be measured directly or indirectly
joint
to measure joint torques directly, place a strain gauge in the ______
muscle
how could you measure joint torques indirectly?
Electromyography (EMG) Isokinetic device
what does indirect measuring, measure?
torque, segment motion (used in physical rehabilitation and for bilateral comparison)
definition: a rigid bar rotating around about an axis or fulcrum
levers
a bone is an example of a ____ and a joint is an example of a _____
bar; fulcrum
the force applied by levers will move a ______
resistance
three types of levers
first second third class levers
example of first class lever, and one example in the body
- see saw - triceps
example of second class lever & one example in the body
- wheelbarrow - calf-muscle
example of third class lever & one in the body
- broom - biceps
which lever is the most common in the body?
third class levers
WHAT CLASS lever is this
what class lever is this?
what class lever is this
2 purposes of levers
- gain mechanical advantage
- gain a greater range of motion
If a moment are of force is longer than the moment arm of resistance, the magnitude or the applied force neede to move a given resistance is less than the magnitude of the resistance. What lever is an example of this?
Second class lever. (few muscles are set up this way, but calf muscles are; wheelbarrow)
If the resistance arm is longer than the force arm, the resistance may be moved through a relatively large distance. What is this an example of?
3rd class levers; most joints in our bodies
mechanical advantage = ?
moment arm force / moment arm resistance
if the mechanical advantage value is:
> 1, < 1 or = 1
> 1 (gain mechanical advantage)
< 1 (lose mechanical advantage)
= 1 (no mechanical advantage)
if the value is > 1, the force required is ____ than the resistance
less
if the value is < 1 the force required is _____ than resistance
greater
most levers in the human body are ____ class and their mechanical advantage is ___ 1.
3rd class; < 1
in the human body lever rom and speed are ______
emphasized
for joint movement to occur in the body muscle frces generated must be in _____ of ______ forces
in excess of resistance forces
definition: the only force component that will cause the bone to rotate around the joint center.
rotary component
the rotary component is ______ to the bone and is known as the __ component
perpendicular; y component
definition: the component of the force parallel to the bone, pulling the bone away from the joint center
dislocating component
definition: the component of force that is parallel to the bone, pulling the bone toward the joint center
stabilizing component
both of the dislocating component and the stabilizing component can be part of the __ component
x
whent a lever has an angle < 90 degrees, it has both a rotary (y) component and a ______ (x) component
dislocating (since its pulling it away from the joint center
when the lever has an angle > 90 degrees, it has both a rotary (y) component and a ______ (x) component
stabilizing (bc its pulling toward joint center)
when the lever has a 90 degree angle, is has a 100% ____ component
rotary component; 100% of the force of the tendon causes rotation
as we move a joint through its range of motion, the muscle that is moving the joint is _____ and more _____ at different joint angles
stronger; stable
the specific joint _____ in which the muscle is stronger/stable ____ from person to person and joint to joint
angles; varies
angles are in reference to the _____ compared to the bone and not bone compared to bone
muscle
the position of the muscle relative to the bone will change the joint ____
angle
force generated (strength) during elbow flexion is highest at __ degrees (joint angle)
80
the _______ of the muscle determines the force generated
length
look at muscle _____ and _______ of the muscle insertion to determine the strongest point
length and angle
definition: condition when a body is completely motionless
static equilibrium
what is an example of static equilibrium
isometric muscle contraction
the net vector sum of static equilibrium is
zero
definition: point about which the body mass or weight is equally distributed and through which the force of gravity acts
center of gravity (CofG)
which method is based on the idea that every segment in the body has its own CoG?
segmental method
locating the center of gravity is important because mechanically, a body behaves as if all of its mass is _______ at the center of gravity
concentrated
when analyzing the human body’s weight as a force for mechanical analyses, the vector representing that force is drawn through the body’s _____ __ ______
center of gravity
understanding the center of gravity is important for what two things?
- stability
- balance
definition: resistance to linear and or angular acceleration
stability
definition: ability to control equilibrium
balance
5 ways to increase stability (KEEP GOING YOURE STUDYING GREAT)
- increase body mass
- increase friction
- increase size of support
- horizontally position the CoG near the edge of support base on the edge of oncoming force
- vertically position CoG as low as possible
definition: resistance to angular acceleration
inertia
inertia depends on mass of ____ and distribution of ____ relative to axis of rotation
body; mass
the closer the mass concentration is to the axis of rotation, the easier it is to…
cause a change in acceleration
what equation do we use when solving for body segments
I = mk squared
definition: prvents the rotating body from leaving its circular path while rotation occurs around a fixed axis
centripetal force
the direction of a centripetal force is always towards the
center of rotation
definition: a force of equal magnitude and opposite in direction created as a reaction to the centripetal force (newtons 3rd law…)
centrifugal force
when gravity is the only acting external force, the angular omentum is ______
conserved
the total H (angular momentum) of the system remains ______ in absence of external torques
constant
while H (angular momentum) is constant, angular velocities may be ________ from one axis or segment to another
transferred
momentum can be transferred from _______ to _______
angular to linear
definition: angular force (torque) acting over some time duration
angular impulse
angular impulse causes predictable changes in ______ ________
angular momentum
Linear vs. Angular
Mass (m) = ?
moment of inertia (I)
Linear vs. Angular
Force (F) = ?
Torque (T)
Linear vs. Angular
Momentum (M) = ?
Angular momentum (H)
Linear vs. Angular
Impulse (I) = ?
angular impulse (Tt)
4 muscles perform knee extension
rectus femoris, vastus medialis, vastus lateralis, mastus intermedius
3 muscles involved in knee flexion
semitendinosis, semimembranosis, biceps femoris
3 muscles ankle dorsiflexion
tibialis anterior, extensor digitorum longus, extensor hallucis longus
3 muscles ankle plantarflexion
gastrocnemius, plantaris, soleus
3 muscles ankle inversion
tibialis posterior, flexor digitorum longus, flexor hallucis longus
2 muscles ankle eversion
peroneus longus, peroneus brevis
3 muscles hip flexion
rectus femoris, iliacus, psoas major
4 musces hip extension
gluteus maximus, semitendinosus, semimembranosis, biceps femoris
