KIN 3514 Exam 2

time between frames is determined by ___

-sampling rate

90 degrees = _____ revs = ____ radians

0.25 revs pi/2 radians

Acceleration

the rate of change of velocity

acceleration is a ____ quantity

vector

what is an issue with the central difference equation?

you lose first and last frames

Key events used as ____ example:

'zero' start time; all time relative to this event ex: heel contact in walking

positive and negative direction in angular calculations

+ counterclockwise - clockwise

sampling rate is provided in ____ time between frames is ___

-Hertz (Hz)- 60 Hz is 60 frames per second -1/frequency : 60 Hz = 0.0167 sec

speed -is ____ - is a ___ quantity -speed =

-is the distance travelled divided by the time it took to travel the distance -scalar -distance/time (m/s)

3D reference systems: -geenrally used in ___ -_____ than 2D -coordinates ____

-motion analysis -much more complex -in ordered triplet (x,y,z)

2D Reference systems: -used for _____ -_____ system -____ axes -can be ____ -point represented by __

-planar motion -Cartesian coordinate -2 perpendicular axes (x and y) -absolute (A) or relative (B) -an ordered pair (x,y)

velocity -is ____ -is a ____ quantity -velocity =

-the rate of change of displacement -vector -displacement / time

180 degrees = _____ revs = ___ radians

0.5 revs pi radians

360 degrees = ____ revs = ___ radians

1 revolution 2 pi

two main reasons why marion jones won the gold medal

1) Marion Jones reached max velocity sooner- initial acceleration is higher 2) at the end of the race, Fynes velocity decreased (and negative acceleration) - you should hit peak velocity and maintain this velocity

three factors affecting projectile motion:

1) projection angle 2) projection velocity 3) projection height

two components to angular acceleration:

1) tangenital acceleration 2) centripetal acceleration

vector operations

1) vector addition 2) vector subtraction 3) multiply vector by scalar

for maximum range, when the relative height of projection is zero, optimum angle is

45 degrees

optimal angle is range is important

45 degrees

gravity accelerates objects toward the earth's surface at ___

9.81 m/s^2

vector subtraction

Adding negative of a vector C = A + B is the same as C = A + (-B)

Multiply vector by scalar

Changes magnitude, not direction

scalar is __ examples

Described by magnitude alone ex: Mass, volume, distance, speed

Vector is ___ examples:

Described by magnitude and direction ex: Displacement, velocity, acceleration

will the direction of the acceleration always correspond with the direction of motion?

NO!

vector addition

Placing tail of 1 vector at the head of another

If theta is very small, the length of the arc can be approximated with ____

a straight line

distance

actual length of path travelled

projection height

affects when projectile will hit apex and contact ground

position

an object's location in space relative to a reference

relative angle

angle between the longitudinal axes of 2 adjacent segments

angular speed

angular distance traveled per unit of time

1 radian is where the ____

arc created by the angle is equal to the radius

vector is represented with ___

arrow magnitude is length, direction where arrow is pointing

why can the projectile equations be used?

because acceleration is constant due to gravity

projection angle

between 0 and 90 degrees; greatest range at 45 degrees

cosine law

c2 = a2 + b2 - 2ABcos(theta)

Central difference equation allows ____

calculation of velocity at the exact frame

collection of kinematic data

camera systems markers outputs marker coordinates accelerometers

point of inflection

change of direction in curvaturue

uses of linear kinematics:

coaching, rehabilitation, ergonomics, research

as you walk faster, your double support _____ and when you run, ___

decreases and when you run you have no double support

conversion from degrees to radians

degrees x pi / 180

coordinate systems is placed at the ____ end of the segment

distal

When recording kinematic data, ordered pairs are provided for ____

each fram

when angular movement is transferred to linear, tangential velocity can be increased by ___

either increasing the angular velocity or increasing the radius of rotation

in general, +ve is ____ and -ve is ____

flexion extension

winter convention ankle angle

foot angle - leg angle - 90 degrees

stride rate

frequency of stepping

only forces acting on an airborne object:

gravity and air resistance

what happens to the vertical velocity throughout the flight of projection?

gravity reduces the vertical velocity until the velocity equals zero at the apex of the trajectory

optimal angle if height is important

greater than 45

for maximum range, when the relative height of projection is below the landing height, optimum angle is

greater than 45 degrees

Vectors can be broken down into ____

horizontal and vertical components

initial gains in speed are due to ____, followed by ____ why?

increases in stride length followed by increases in stride rate we have anatomical limitations; we can't take an infinite step; as we approach anatomical limitation, we have to increase speed by increasing rate of stride

steepness of slope provides an indication of ____. steeper = ____ zero slope = ____

indication of the velocity higher velocity zero velocity

what happens to the horizontal component of the projection velocity throughout the flight of projection?

it remains constant

optimal angle if distance is important

less than 45

for maximum range, when the relative height of projection is above the landing height, optimum angle is

less than 45 degrees

tangenital velocity

linear velocity behaves as an instantaneous tangent to the trajector

in angular motion, do all points go through the same linear displacement?

no

Are acceleration and motion in the same direction?

not always

the trajectory is shaped like a

parabola

linear velocity is always ____

perpendicular to the rotating segment

local extrema

points on the graph where acceleration and velocity are zero

conversion from radians to degrees

rad x 180 / pi

linear displacement is dependent on ___

radius of rotation

tangenital velocity is dependent upon ____

radius of rotation

angular velocity

rate of change of angular displacement

does relative or absolute angles describe flexion/extension about a join?

relative

in the winter convention,

relative angles are calculated from absolute angles

slope

rise / run or delta S / delta T

radians theta =

s/r

distance is a ____ quantity

scalar

displacement

straight line between 2 positions

linear kinematics can be a __ or ___ path

straight or curved

joint angle is defined as

the angle between adjacent segments

calculating the velocity between two frames actually determines

the average velocity between the two frames

stride length

the distance between heel contacts in the same limb

the range or distance the projectile travels is determined by

the product of the horizontal velocity and the flight time

step

the time interval between an event on one leg to the same event on the opposite leg

stride

the time interval from an event on one limb to the same even on the same limb

what is a limiting factor about relative angles?

they cannot be used to describe how segments are oriented in space

winter convention knee angle

thigh angle mine leg angle

winter convention hip angle

thigh angle minus trunk angle

linear kinematics

translational motion occurring over time

displacement is a ___ distance is a ____

vector scalar

acceleration = units of acceleration

velocity / time m/s^2

three equations

vf = vi + at s = vi x t + at^2 vf^2 = vi^2 + 2as

camera systems to collect kinematic data

video optoelectronic high speed

central difference equation

vx = x (i +1) - x (i-1) / 2x deltaT vy = y (i+1) - y (i-1) / 2x deltaT

double support definition and %

when both limbs are in contact with ground (~10%)

swing definition and %

when the limb is airborne (~40%)

stance definition and %

when the limb is in contact with the group (~60%)

Linear kinematics is concerned with ____, not _____

with spatial and temporal characteristics (position, velocity, acceleration) not the forces that cause these movements

projection velocity components

x and y components in flight, the x component is constant and the y component is changing due to gravity

cos theta =

x-component / a

sin theta =

y-component / a

can velocity be both positive and negative?

yes since it is a vector