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153 Cards in this Set
- Front
- Back
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medial rotation occurs around what axis?
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superior-inferior
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hyperflexion occurs around what axis?
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mediolateral
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plantar flexion is a fundamental movement of what plane?
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sagittal
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radial deviation is a fundamental movement of what plane?
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frontal
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pronation is a fundamental movement of what plane?
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transverse
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adduction is a fundamental movement of what plane?
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frontal
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left rotation is a fundamental movement of what lane?
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transverse
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horizontal abduction is a fundamental mvement what what lane?
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transverse
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what is the functional classification of a shoulder joint?
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triaxial
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what is the functional classification of knee joint?
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biaxial
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Biomechanics definition
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the fundamentals of body movement and the way the body works in order to make such movements and how those movements affect the body.
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method for representing vector quantity:
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magnitude = "size" of vector = vector's displacement. - scalar portion of the vector - represented by length of vector - vector has both magnitude and direction - direction indicates how vector is oriented relative to some reference axis (degrees)
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vector quantity
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quantity that has both magnitude and direction
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scalar quantity
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a quantity that has magnitude only.
ex: time, speed, temperature NO directional component ONLY magnitude. ex: density, mass, and energy |
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scalar vs. vector
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scalar = no directional component, only magnitude
vector = magnitude and direction |
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kinematic
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The branch of mechanics dealing with the study of the motion of a body or a system of bodies without consideration given to its mass or the forces acting on it.
*science and measurements to study body movements |
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kinetic
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motion - movements made by the body and force
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What is the center of gravity? does the COG have to be in the geometric center of the object?
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the COG is the core area that helps a person balance. it does NOT have to e in the geometric center.
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Center of gravity
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the point through which the resultant of gravitational forces on a body passes and from which the resultant force of attraction of the body on other bodies emanates: coincident with the center of mass in a uniform gravitational field.
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Newton's First Law - Law of inertia
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a body at rest will remain at rest, and a body in motion will remain in motion with a constant velocity, unless acted upon by a force.
EX: the more force i kick a soccer ball with the farther it will go |
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Newton's second law - law of acceleration
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a force acting on a body is equal to the acceleration of that body times its mass.
force = mass x acceleration EX: pushing an empty grocery cart is faster and easier than pushing a full, heavy grocery cart. |
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Newton's third law - law of action and reaction
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for every action there is an equal and opposite reaction. if one body exerts a force F on a second body, the first body also undergoes a force of the same strength but in the opposite direction. This law lies behind the design of rocket propulsion, in which matter forced out of a burner at high speeds creates an equal force driving the rocket forward.
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Newton's first law applied in biomechanics - law of inertia
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by increasing workout intensity during each visit to the gym, stamina builds so that that body can handle more intense workouts.
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what will cause acceleration of an object? how?
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force. when force is applied on an object it creates movement that can cause acceleration.
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what determines movement or no movement?
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force
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ground reaction force
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the reaction to the force the body exerts on the ground
EX: a person standing on the ground exerts a contact force on it (equal to the person's weight) and at the same time an equal - l and opposite ground reaction force is exerted by the ground on the person. - newtons 3rd law |
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a person walks 4 km south, then turns and walks 4 km west, then turns and walks 2km north, and then turns west and walks 1 km. what were the linear distance and the linear displacement?
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linear distance = 4 + 4 + 2 + 1 = 11 (all of the distances added up)
linear displacement = 4 |
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how much force must be exerted to accelerate a 20 kg weight to 7.21 m/s^2?
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F = M x A
= 20 x (7.21) |
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a high jumper takes off with a velocity of 7 m/s at an angle of 70 to the horizontal.
what is the jumpers initial horizontal velocity? |
h = 7 cos 70
= 2.39 m/s |
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a high jumper takes off with a velocity of 7 m/s at an angle of 70 to the horizontal.
what is the jumpers initial vertical velocity? |
v = 7 sin 70
= 6.58 |
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A person standing vertical jumping height is 0.75 m.
what would be his take-off velocity? |
vf^2 = vi^2 + 2ad
0 = vi^2 + 2 (-9.81) (0.75) 0 = vi^2 - 3.84 = vi^2 = 3.84 m/s |
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a person's standing vertical jumping height is 0.75
what would be his total hang time? |
d = Vit + 0.5 at ^2
0.75 = 0 + 0.5 (9.81) + 2 t = 0.391 sec ^ 2 total hangtime = 0.782 |
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diagram of how leg moves when walking the percent of time in different phases of gait. what kinematic variables can be determined?
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temporal phase and angular displacement
time - relative time - % of total stride time is given temporal phases - stance and swing position - knee and ankle |
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an avulsion fracture is most likely due to what type of loading?
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tension
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as the velocity of an eccentric contraction increases the ability to generate force - increases or decreases?
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increases
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as the velocity of a concentric contraction increases the ability to generate force - increases or decreases?
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decreases
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material properties
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depends on material type
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structural properties
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depends on material type and geometry
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Pennate Muscles are capable of exerting more force than non-pennate muscles of similar size
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pennate muscles = opposite of parallel - fibers run diagonally to the axis of movement
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what factors affect muscle force output?
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fiber type, force-length relationship, muscle architecture, rate of motor unit activation
NOT : muscle insertion angle |
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how are stress and strain related?
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proportional to eachother
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stress
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pressure or tension exerted on a material object. degree measured in units of force per unit area.
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strain
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a force tending to pull or stretch something to an extreme or damaging degree. magnitude of a deformation, equal to the change in the dimension of a deformed object divided by its original dimension
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factors that affect muscle torque output
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moment arm
physiological - fiber type, CSA biomechanical - muscle architecture, force-length, force velocity neural |
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during the last step of a high jump, a 50 kg jumper contacts the ground with a net vertical force of 250 N and a vertical velocity of -3 m/s over 0.17 s. what is his take of velocity?
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*from relationship of impulse and momentum
F x t = ^ (mv) vi = -3 t = 0.17 s m = 50 k F = 2500 N vf = ? (2500N)(0.17s) = 50 kg (Vf - (-3 m/s)) Vf = 5.5 m/s |
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Suzie Lavtaski (m = 56 kg) is skiing at Blue Mountain. She is moving at 16 m/s across the crest of a ski hill located 34 m above ground level at the end of the run. Determine Suzie's kinetic energy
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KE = -1/2 mv^2
= 1/2 (56) (16)^2 = 7168 J |
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Lamar Gant, U.S. powerlifting star, became the first man to deadlift five times his own body weight in 1985. Deadlifting involves raising a loaded barbell from the floor to a position above the head with outstretched arms. Determine the work done by Lamar in deadlifting 300 kg to a height of 1.9 m above the ground.
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W = ^ (KE) = mg (sin theta) d
m = 300 kg d = 1.9 m F x D x 0cos theta = (300 x 9.8) (1.9) (0cos theta) = 2940N x 1.9 x o cos theta = 5586 J |
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The taipei 101 in Taiwan is a 1667-foot tall, 101-story skyscraper. the skyscraper is home to the world's fastest elevator. the elevators transport visitors from the ground floor to the observation deck on the 89th floor at speeds up to 16.8 m/s. Determine the power delivered by the motor to lift the 10 passengers at this speed. the combined mass of the passengers and cabin is 1250 kg.
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h = 1667 f
v = 16.8 m/s m = 1250 kg p = w/t = (fd)/t = f x v f = mg = 12,250 N x 16.8 m/s = 210,000 W |
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chloe leads North's varsity softball team in hitting. in a game against New Greer Academy this past weekend, Chloe slugged the 181-gram softball so hard that it cleared the outfield fence and landed on Lake Avenue. At one point in its trajectory, the ball was 28.8 m above the ground and moving with a speed of 19.7 m/s.
determine the total mechanical energy of the softball. |
m = 181 g
s = 19.7 m/s h = 28.8m KE + PE = total ME KE = 1/2 mv^2 = 1/2 (.181kg)(19.7 m/s) = 25.1221 J PE = mgh = (.181kg)(9.81)(28.8) = 51.137 J KE + PE = 35.1221 + 51.137 |
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A 62.1-kg male ice skater is facing a 42.8-kg female ice skater. they are at rest on the ice. they push off each other and move in opposite directions. the female skater moves backwards with a speed of 3.11 m/s. determine the post-impulse speed of the male skater.
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(62.1 kg) x v + (-1.33 x 11kg x m/s) = 0
v = (133.11kg x m/s) / 62.1kg = 2.14 male : 62.1 kg x V female : (42.8kg)(-3.11) = -1.22.11 v = 2.14 ms |
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a 25 kg box is pulled up a rough inclined surface by a constant force of Fp = 200N which is applied parallel to the incline. the incline makes an angle 25 degrees with the horizontal and the coefficient of friction between the incline and the block is 0.25. if the block is displaced by 15 m, determine the work done on the block by pulling force, by the force of friction, and by the force of gravity. what is the net work done on the box?
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m = 25kg, Fp = 200N, theta = 25 degrees, u = .25, L = 15m
WFwx = -mg sin theta L = -(25)(9.81)(sin25)(15) =-1554.71 J WF = PL = 200N (15m) = 3000J WFf = -FfL = umg cos theta L = -(.25)(25)(9.81)(cos25)(15) = -833.52J W = WF + WFf + WFwx = 3000 - 833.52 - 1554.71 = 611.77J |
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a figure skater is attempting a jump in which she performs 3 revolutions while in the air. she leaves the ice with a velocity of 7 m/s at a projection angle of 30 degrees. how long will she be in the air? if she spins at 3 revolutions per second, will she be able to complete all 3 revolutions before landing?
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Vo = 7 m/s
theta = 30 degrees Vi = 7 m/s sin30 = 3.5 n = ho + 3.5t = -4.9t^2 0 = 0 + 3.5t - 4.9t^2 0 = t (3.5 - 4.9t) t - 3.5/4.9 = 0.714 No - she will not be able to complete all three revolutions |
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an object with a mass of 100 kg cannot be lifted unless the force applied is greater than 981N
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true - gravity at least 9.81
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horizontal velocity of a projectile is NOT affected by gravity
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factors that affect trajectory of a projectile: angle of projection, projection velocity, relative height of projection
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Mechanical work can be computed by measuring the change in energy
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work = force x distance
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the moment arm is NOT always measured from the point of application of the force to the axis of rotation
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measurement of moment arm = The perpendicular distance from an axis to the line of action of a force.
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the sum of torques about the center of mass of an object always equals zero
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moment arm = o
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Free Body Diagram
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a stick figure drawing of the system showing the vector representations of the external forces acting on the system
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ground reaction force
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force exerted by the ground on a body in contact with it
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Friction forces
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friction is a force that acts parallel to the surface and opposite to the direction of motion or of impending motion
"u" is the coefficient of friction "FN" is the normal force or the force perpendicular to the surface NOT - the area of contact influences the friction force |
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components of magnitude of drag force
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nature of fluid
nature and shape of object velocity of the object through the fluid |
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if a tennis ball dropped from a 1 m height and it rebounded to 58 cm from a concrete surface what would be coefficient of restitution?
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0.76
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coefficient of restitution
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bounciness of an object - fractional value representing ratio of velocities after and before and impact. COR of 1 collides elastically. less than 1 collides inelastically.
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impulse
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force applied over time
the area under the force time curve |
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two ice dancers are at rest on the ice, facing each other with their hands together. they push off on each other in order to set each other in motion. the subsequent momentum change (magnitude only) of the two skaters will be - ?
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the same for each skater
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momentum conservation
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principle stating that total linear momentum of an isolated system remains constant regardless of changes within the system
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magnitude of torque can be changed by changing - ?
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magnitude of force
direction of force point of application of force |
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when the person moves from arms down by sides to hands above hand - total body center of gravity does what?
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moves up
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if the shoulder point is (2,10) and the wrist point is (2.1) locate the COM of the arm given the following: arm COM located 33% from shoulder
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arm COM coordinates are (2,7)
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The center of mass of an object is ???
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the balance point of a system
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primary factors that influence the trajectory of projectile?
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projection velocity vector, projection angle, projection height
NOT projection distance |
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Soccer ball has been kicked with a velocity of 25 m/s at an angle of 30 degrees above the horizontal axis and is traveling from left to right.
calculate the vertical and horizontal velocity components |
Vix = Vi x cos30
Viy = Vi x sin30 |
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Soccer ball has been kicked with a velocity of 25 m/s at an angle of 30 degrees above the horizontal axis and is traveling from left to right.
calculate the height of the trajectory |
Vfy^2 +2aydy
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Soccer ball has been kicked with a velocity of 25 m/s at an angle of 30 degrees above the horizontal axis and is traveling from left to right.
what is the total flight time from time 1 to time 2? |
dy = Viyt + 1/2ayt^2
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Soccer ball has been kicked with a velocity of 25 m/s at an angle of 30 degrees above the horizontal axis and is traveling from left to right.
what is the range of flight from time 1 to time 2? |
Vix = d/t
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concentric
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force output decreases as velocity of shortening increases
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is bicep curl a good exercise?
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yes - there is a full range of motion and the resistive torque changes on the upward and downward phase so more work is done.
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Shoulder joint (glenohumeral)
-move humerus in sagittal plane anterior movement? name of the posterior movement beyond anatomical position? |
anterior movement - flexion
posterior movement - hyperextension |
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Shoulder joint (glenohumeral)
-move the humerus in the frontal plane name of movement away from midline of body? name of movement toward midline of body? axis of movement? |
away - abduction
toward - adduction axis - anteroposterior |
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Shoulder joint (glenohumeral)
-move the humerus in the transverse plane name the movement as the anterior aspect turns to face medially? laterally? axis of movement? |
medially - medial rotation
laterally - lateral rotation axis - superior-inferior |
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Shoulder joint (glenohumeral)
-move the upper extremity in such a way that a circle is described by the tips of the fingers. circumduction - combination of what fundamental movements? |
flexion-extension
abduction-adduction |
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Shoulder joint (glenohumeral)
-from a position of 90 degrees of shoulder joint abduction (elbow extended), move the humerus toward the midline of the body in the transverse plane about a longitudinal axis. what is the name of this movement? |
horizontal adduction
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Shoulder joint (glenohumeral)
move the humerus away from the midline of the body in a transverse plane about a longitudinal axis. what is the name of this movement? |
horizontal abduction
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Shoulder joint (glenohumeral)
functional classification? |
triaxial
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elbow joint (humeroulnar)
-move the forearm (radius and ulna) in the sagittal plane. name of anterior movement? return movement? |
anterior - flexion
return - extension |
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elbow joint (humeroulnar)
-are frontal and transverse plane movements possible at the elbow joint? |
no
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elbow joint (humeroulnar)
functional classification? |
uniaxial
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radioulnar joint
- moving from fundamental standing position to anatomical position requires you to place the radioulnar joint in what position? |
supination
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radioulnar joint
-name the movement of turning the forearm and palm at the radiulnar joints toward the posterior side of the body |
pronation
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radioulnar joint
functional classification? |
uniaxial
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wrist (radiocarpa, intercarpal, ulnar-disktriquetral)
- move hand in sagittal plane name of anterior movement? axis of movement? |
anterior movement - flexion
axis - medio-lateral |
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wrist (radiocarpa, intercarpal, ulnar-disktriquetral)
-move hand in the frontal plane name of movement away from the midline of the body in which the hand is toward the radius? |
radial deviation
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wrist (radiocarpa, intercarpal, ulnar-disktriquetral)
-name of the movement in which the hand is moved toward the ulna? |
ulnar deviation
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wrist (radiocarpa, intercarpal, ulnar-disktriquetral)
-with radius and ulna firmly fixed, can transverse plane movement occur? |
NO
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wrist (radiocarpa, intercarpal, ulnar-disktriquetral)
- with the radius and ulna still firmly fixed, can you describe a circle with the hand? name of movement? |
YES
name of movement - circumduction |
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wrist (radiocarpa, intercarpal, ulnar-disktriquetral)
functional classification? |
biaxial
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hip joint (pelvis fixed) move thigh at hip joint
- movements that occur in sagittal plane? |
flexion, extension, hyperextension
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hip joint (pelvis fixed) move thigh at hip joint
-movements that occur in frontal plane |
abduction, adduction, hyperadduction
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hip joint (pelvis fixed) move thigh at hip joint
-movements that occur in the transverse plane |
medial and lateral rotation, horizontal adduction, horizontal abduction
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hip joint (pelvis fixed) move thigh at hip joint
-can circumduction be performed at this joint? |
YES
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hip joint (pelvis fixed) move thigh at hip joint
- from a position of 90 degrees of hip flexion (knee flexed to 90 degrees), move the femur toward the midline of the body in the transverse plane about a longitudinal axis. what is the name of this movement? |
horizontal adduction
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hip joint (pelvis fixed) move thigh at hip joint
- move the femur away from the midline of the body in the transverse plane about a longitudinal axis. what is the name of this movement? |
horizontal abduction
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hip joint (pelvis fixed) move thigh at hip joint
functional classification? |
triaxial
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Knee joint
- move the tibia and fibula in sagittal plane. name of posterior movement? axis of movement? |
posterior - extension
axis - medio-lateral |
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Knee joint
- with the knee flexed (as in sitting position), rotate the tibia and fibula so that the anterior aspect of the leg turns medially and then laterally. name of medial movement? name of lateral movement? |
medial - medial rotation
lateral - lateral rotation |
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Knee joint
functional classification |
biaxial
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ankle joint (talocrural)
-move foot in a sagittal plane name movement in which the dorsal surface of the foot moves toward the anterior aspect of the leg? name the movement in which the dorsal surface of the foot moves away from the anterior aspect of the leg? |
toward - dorsiflexion
away - plantar flexion |
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ankle joint (talocrural)
functional classification |
uniaxial
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intertarsal joints (subtalar, midtarsal)
-move the foot so the sole faces medially. what is the name of this movement? |
inversion
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intertarsal joints (subtalar, midtarsal)
-what is the name of the movement in the opposite direction, in which the sole is turned to face laterally? |
eversion
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intertarsal joints (subtalar, midtarsal)
functional classification? |
intertarsal joints (subtalar, midtarsal)
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wrist joint
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functional classification - biaxial
movements permitted - flexion, extension, hyperextension; radial and ulnar deviation; circumduction planes of motion associated with identified movements: sagittal and frontal axes of motion associated with identified movements: mediolateral and anteroposterior |
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radioulnar joint
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functional classification - uniaxial
movements permitted - pronation, supination planes of motion associated with identified movements:transverse axes of motion associated with identified movements: longitudinal |
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elbow joint
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functional classification - uniaxial
movements permitted - flexion, extension planes of motion associated with identified movements:sagittal axes of motion associated with identified movements: mediolateral |
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shoulder joint
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functional classification - triaxial
movements permitted - flexion, extension, hyperextension, abduction, adduction, medial and lateral rotation; horizontal adduction and abduction; circumduction planes of motion associated with identified movements:sagittal, frontal, transverse axes of motion associated with identified movements: Mediolateral and anteroposterior, longitudinal |
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hip joint
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functional classification - triaxial
movements permitted - flexion, extension, hyperextension, abduction, adduction, medial and lateral rotation; horizontal adduction and abduction; circumduction planes of motion associated with identified movements: sagittal, frontal, transverse axes of motion associated with identified movements: mediolateral, anteroposterior, longitudinal |
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knee joint
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functional classification - biaxial
movements permitted - flexion, extension, hyperextension, medial and lateral rotation planes of motion associated with identified movements: sagittal, transverse axes of motion associated with identified movements: Mediolateral, longitudinal |
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ankle joint
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functional classification - uniaxial
movements permitted - dorsiflexion, plantar flexion planes of motion associated with identified movements:sagittal axes of motion associated with identified movements: mediolateral |
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MCP/MTP
(all metatarsophalangeal/metacarpophalangeal joints except MCP 1 |
functional classification - biaxial
movements permitted - flexion, extension, hyperextension, radial and ulnar deviation; circumduction planes of motion associated with identified movements: sagittal, frontal axes of motion associated with identified movements: mediolateral, anteroposterior |
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PIP/DIP
all proximal interphalangeal/distal interphalangeal joint |
functional classification - uniaxial
movements permitted - flexion, extension, hyperextension planes of motion associated with identified movements: sagittal axes of motion associated with identified movements: mediolateral |
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Biceps curl - movement analysis
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joint movement: elbow/upward phase (starting with dumbbells in a lowered position
start position - anatomical movement joint action - flexion ~110 degrees plane - sagittal axis - mediolateral joint/movement: shoulder/upward phase start position - anatomical position joint action, plane, axis - N/A |
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Shoulder Press (wide grip)
joint movement - elbow/upward phase (starting with dumbbells in a lowered position) |
start position - ~110 degrees
joint actions - extension plane - sagittal axis - ML |
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Shoulder Press (wide grip)
joint movement - elbow downward phase (starting with dumbbells in an elevated position) |
starting position - extended 180 degrees
joint action - flexion plane - sagittal axis - ML |
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Shoulder Press (wide grip)
shoulder upward phase (starting with dumbbells in a lowered position) |
start position - abducted ~70-90 degrees
joint actions - abduction plane - frontal axis - AP |
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shoulder press (wide grip)
shoulder downward phase (starting with dumbbells in an elevated position |
start position - abducted ~180 degrees
joint actions - adduction plane - frontal axis - AP |
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5 primary kinematic variables and measurements:
TIME - TEMPORAL ANALYSIS |
Time variables are the most basic analysis. they answer the questions When? How often? In what order? How long?
Cadence is the example of time variables in walking (how many steps per minute or per second?), stride time (how long does it take to complete a stride?), and temporal patterning. Temporal patterning refers to the timing of events relative to other events. Absolute time - actual time measurement (e.g. race duration, phase duration, etc.) Relative time - % of total time (relative time = segment or phase duration divided by total time) |
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5 primary kinematic variables and measurements:
POSITION |
It is defined as a location in space relative to some reference point or reference frame. In order to describe where something is, we must have a defined starting point. We can define position in linear and angular terms. To define the location of a point for linear motion, we typically use x,y,z coordinates, where x and z are describe horizontal position, and y describes vertical position. To define the location of a point or line for angular motion, we typically describe the angle at which the point or link lies relative to the zero degree point.
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5 primary kinematic variables and measurements:
DISPLACEMENT AND DISTANCE |
Displacement and distance represent similar concepts, but they are not exactly the same.
Displacement is a vector quantity, which means it is defined in terms of both magnitude and direction. Distance is a scalar quantity, which means it is defined in terms of magnitude only. Because of this difference in nature, they are defined differently as well Displacement is defined as the final change in position Distance is defined as the sum of all change in position. |
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5 primary kinematic variables and measurements:
SPEED AND VELOCITY |
Speed is defined as the rate of change of distance. It is a scalar quantity.
Velocity is a vector corresponding to speed. velocity is the rate of change of displacement, and usually qualified by a directional adjective like horizontal, vertical, resultant. |
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Newton's Laws - physiological systems
First Law - law of inertia |
swimmer on starting blocks will remain at rest until they hear gun and exert force to push off blocks.
bicycle rider must exert muscular force in order to keep their bicycle at a constant velocity because the force of drag and friction act to slow the rider |
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Newton's Laws - physiological systems
second law - law of acceleration |
biceps brachii must exert force in order for the mass of the forearm to be accelerated (arm flexion).
a bowler must exert more force when using a heavier ball if the same acceleration is desired. |
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Newton's Laws - physiological systems
third law - law of action and reaction |
when a rock climber is hanging from a handhold the rock exerts a force that is equal to the climber's body weight but pointed vertically.
when a hockey player holds their stick the stick exerts a force equal to the grip force but directed outward from the palm of the hand. |
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torque diagram - leg curl
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joint action: down - extension. up - flexsion
motive force: down - weight. up - muscle resistive force: Down - muscle. Up - weight FMG Developing force: Down - knee flexors. Up - knee flexors Muscle action: Down - eccentric. Up - concentric Agonist: Down - knee flexors. Up - knee extensors antagonist: Down - knee extensors. Up - knee flexors Joints to be stabilized: hip, torso, ankle |
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what factors affect the muscle torque output in example of leg curl?
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moment arm - depends on muscle insertion angle
muscle force: physiological factors (CSA, muscle fiber type). Neural factors. biomechanical factors (fiber architecture - pennate exert more force. non-pennate have a greater range of motion and faster contraction velocity. Force-length relationship - optimum force generation is at 110-120% of resting muscle length. Force-velocity - for concentric contraction as velocity increases force decreases. For eccentric contractions we exert more force (resist heavier weight) when the velocity is more negative |
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Identify areas of passive and active insufficiency in the performance of the LEG CURL.
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active insufficiency is present when the knee is fully extended. the muscle is active and fully contracted at this point. the sarcomeres are compressed leading to a decrease in the ability to generate force.
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explain the relationship between the speed of the movement and the amount of weight that can be lifted
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force-velocity - for concentric contraction as velocity increases force decreases.
for eccentric contractions we exert more force (resist heavier weight) when then velocity is more negative |
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Is the bicep curl a good exercise?
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yes there is a close match between the resistive torque and the muscle torque (strength curve)
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resistive torque for a bicep curl performed eccentrically
= ? |
performing bicep curl eccentrically moves the resistive torque above the muscle torque
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Environmental and physiological constraints associated with shoveling snow
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environmental - snow density, water content, amount of snow, large driveway vs. small driveway, snow shovel characteristics, handle length, shape, distance needed to be moved.
physiological - muscle strength, physiolgical, neural, biomechanical, MIA, endurance, technique/skill |
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mobility
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the degree to which the bones are allowed to move before being restricted by surrounding tissues
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stability
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the ability of a joint to resist displacement or dislocation; the strength of the bonds between the bones in a joint
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gravitational potential energy
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the energy of the mass of an object by virtue of its position relative to the surface of the earth
potential energy = m * g * h |
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energy - the capacity to do work
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the energies of motion are linear and angular kinetic energy
KE t = 1/2 M * V^2 KE T = 1/2 L * W^2 |
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impulse (mechanical variables to standardized gait cycle)
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force exerted over time
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momentum (mechanical variables to standardized gait cycle)
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quantity of motion on a body and a product of mass and velocity
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weight (gravity)
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attractive force that earth exerts on body
weight = mag (product of mass and the acceleration of gravity = 9.81) weight of an object Fw is gravitational force acting down on object normal force Fn of an object thats being supported by surface is the component of the supporting force that is perpendicular to surface |
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drag
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resistance to movement through fluid
ex: you have been hired by lance armstrong to be a part of his team. minimize the forces that resist lance's forward motions Fdrag = 1/2 p v^2 CdA decrease frontal area decrease drag coefficient |
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4 - a person doing a seated leg curl with load of 10 kg and he extends his knee to exercise the quad muscles
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draw normal and tangential components
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23 - on the figure, diagram the muscle force components. your figure should include muscle force, mechanical axis, normal and tangential forces and muscle insertion angle. identify rotary and linear effect and determine if linear effect is stabilizing or dislocating
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mechanical axis - represent moving bone with a single line
muscle force vector - start (tail) on insertion on moveable bone. arrow directed along fibers tangential force - parallel to mechanical axis, extend in the direction that will let you make a triangle with Fn to the tip of Fmuscle MIA great than 90- linear effect = stabilizing component. |
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resolving muscle force vectors
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normal (perpendicular) force (Ft) = rotary component
tangential force = linear effects. stabilizing component. dislocating component |
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vector resolution
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taking a resultant vector and brewing it down into 2 or more component vectors
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vector composition
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process of determining a resultant vector from two or more vectors
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vector algebra
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a vector quantity is represented by an arrow. length represents magnitude. arrow represents direction
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