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

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Published on 22 Apr 2013

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

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

## 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.