Kinesiology 2241A/B Study Guide - Final Guide: Angular Velocity, Angular Acceleration, Moment Of Inertia

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Published on 22 Apr 2013
School
Western University
Department
Kinesiology
Course
Kinesiology 2241A/B
Professor
Biomechanics Final Review
Pattern: run jump ect, movement pattern
Skill: pattern adapted to a task
Technique: variations of a skill ex. Jump serve
Style: unique timing or specialized moves
Constraints: anything limiting can be human or event
Closed skill: predictable environment for example a free throw, you are using
biomechanical principles
Open skill: unpredictable, execution less ideal
Continuous: can be broken down into discrete but as a whole doesn’t have a definite
begging or end
OPO: is the goal of a movement, for example getting as high up as you can
Biomechanical principles: factors affecting muscle forces (length tension relationship
between muscles) momentum, radius of body parts, kinetic link being used, lift and drag
forces, angle of projection/attack/attitude, rebound and spin of an object, methods of
initiating body rotation
Analysis process: 1. divide into discrete parts 2. mechanical purpose of each part (each
parts opo) 3. biomechanical factors (acceleration, radius ect.) 4. biomechanical principles
to achieve BP 5. critical features necessary for movements of specific skill
Force arm: needs to be not inline with c of g because then you will not create any torque
on the body
Factors influencing movement: magnitude of net torque has a big effect, the amount
created will effect the inertial characteristics of the object in ways or its rotational inertia
or friction factors or the pathway available
Rotary motion: represented by a straight line which starts at the axis of rotation and then
draw it right out to where it rotates therefore you are drawing it out to where it rotates
therefore you are making the radius, both points have the same angle thus the same
angular distance but since the second has a greater linear distance it has a greater linear
velocity
Angular velocity: how fast a rotating body segment changes its position, measured in
radian or degrees/second, 1 radian = 57.3 degrees, either clockwise or counter clockwise
Angular acceleration: rare in human motion, it is equal to angular velocity plus torque, a
large change in angular acceleration causes a great change in angular velocity, where a
small change causes a s small change in angular velocity over a long time, it equal
change in angular velocity over change in time
Average angular velocity: time it takes for a body/segment/object to complete a motion,
useful in quantitative analysis of motion, it equals angular displacement/time, it is an
average for the entire time of the motion
Instantaneous angular velocity: the angular acceleration at a particular point in the ROM
it is equal to radius times angular acceleration, it determines the instantaneous velocity of
any point on a system, you take this off the tangent
R of rotation: symmetrical systems distance from axis of rotation to a precise point on a
rotating system
R of gyration: asymmetrical therefore most objects, distance from axis of rotation to a
point where all the mass is concentrated, it is I=mk(2) or I=mr(2), if mass is spread far
from axis it has a larger radius of gyration
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Angular momentumL L=inertia times angular acceleration, cant change without external
torque, I is the rotational inertia therefore the bodies resistance 2 change, changing the
inertia will change the angular acceleration drastically
Angular impulse: Tt it is the torque multiplied by time of torque applied, no external
torques can be applied while airborne therefore takeoff is very important, determines
amount of angular momentum created
Conservation of angular momentum: L-Iw, L will stay the same while airborne therefore
you can either change angular accerlation by changing the inertia (smaller position) or
opposite, think of the diver
Turntable demos: twists about longitudinal axis, spins about a-p axis as get smaller you
move faster
Throw pattern: object behind body, sequential for increased high end point velocity,
curvilinear path, mostly wheel-axle, open kinetic link (sequential from larger to smaller)
max distance or velocity, you create angular momentum during the initial seg of body
rotation
Push pattern: all segments behind object simultaneous to increase force, rectilinear path,
mostly lever motions, closed kinetic link, everything moves together
Constraints to throw/push continuum: mass of projectile, volume/size/shape/profile,
target area, strength/power/skill of person
Open kinetic chain: throw or kick, end segment free (e.g. hand) sequential movement
Closed kinetic chainL jump/push end segment restrained, simultaneous
Steps of throw: 1.proximal 2.distal lags behind 3. achieve either max distance for velocity
Magnitude of radius: is influenced by mass of object
Final velocity: final v of hand at the end will determine projective v, the radius is the
perpendicular distance from axis of rotation and release point, the kinetic link will also
effect as will the radius
Kinetic link characteristics: more massive segments at proximal end least massive at
distal end, initial motion caused by torque applied 2 base
Sequential motions: 1.proximal/massive self giving L 2. external T decelerates into
proximal segment 3. to conserve L next segment acceleration (has smaller k) no increase
in momentum just maintain velocity 4. Each successive segment acierates therefore
increase angular acceleration than previous segment due to both the radius getting smaller
and trying to maintain velocity
Airborne reaction rotation: if u initiate a rotation about an axis it will happen opposite
direction at same axis (law of conservation)
Lever motions: flexion/extension/protraction/retraction/abd/adduction. Force creating
Wheel-axle: medial/lateral rotation, prontation/supintion, inversion.eversion, muscle
torque rotates a bone which becomes an axle, wheel is adjacent segment position at an
angle 2 the axle, creates velocity
Mechanical purpose of PUSH: max force/max power (force x velocity) max accuracy
Push pattern + force activates: max strength movements demands simultaneous
segmental rotations, move in rectilinear path, minimize accerlation in movements 2 avoid
injury
Push pattern + power activities: need both force and velocity to move fast, need higher
force in a short time
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Document Summary

Constraints: anything limiting can be human or event. Closed skill: predictable environment for example a free throw, you are using biomechanical principles. Continuous: can be broken down into discrete but as a whole doesn"t have a definite begging or end. Opo: is the goal of a movement, for example getting as high up as you can. Biomechanical principles: factors affecting muscle forces (length tension relationship between muscles) momentum, radius of body parts, kinetic link being used, lift and drag forces, angle of projection/attack/attitude, rebound and spin of an object, methods of initiating body rotation. Analysis process: 1. divide into discrete parts 2. mechanical purpose of each part (each parts opo) 3. biomechanical factors (acceleration, radius ect. ) 4. biomechanical principles to achieve bp 5. critical features necessary for movements of specific skill. Force arm: needs to be not inline with c of g because then you will not create any torque on the body.

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