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Biomechanics Exam 3 > LINEAR KINEMATICS > Flashcards

LINEAR KINEMATICS Flashcards

1
Q

kinematics

A

concerned with motion of objects without reference to the forces which cause the motion
-what you can SEE

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2
Q

passive marker-based motion capture

A

-put a bunch of markers on body + track them with video cameras around the room
-markers on the body aren’t sensors because they don’t emit their own light; they reflect light back to the cameras that capture their position
-the camera is what emits light, the marker just reflects it

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3
Q

where do we place the markers in passive marker-based motion capture

A

on bony landmarks
-because we are tracking SKELETAL motion

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4
Q

how many cameras are needed to get xyz coordinates

A

minimum 2 cameras

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5
Q

how many dimensions in passive marker-based motion capture

A

3D reconstruction of 2D images
-multiple cameras collect different perspectives

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6
Q

what is the camera made of

A

infrared LEDS + lens with infrared filter
-infrared light shines onto marker, which sends reflected light back to the camera

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7
Q

in passive marker-based motion capture we sample continuous/discrete time points

A

discrete

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8
Q

frame rate

A

sampling frequency
-how frequently the camera is taking an image

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9
Q

if you have a fast movement, you want a slower/faster frame rate

A

faster
-otherwise you will miss some of the movement

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10
Q

shutter speed

A

time the shutter is open

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11
Q

fast shutter speed = too light/dark

A

dark but clearer

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12
Q

time series data

A

a collection of. observations for a single subject at different time intervals
-generally equally spaced

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13
Q

noise

A

-points that wiggle around the true value
-fluctuations in the data that aren’t real

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14
Q

distance

A

length traveled along a path
-cumulative across changes in direction

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15
Q

is distance a scalar or vector

A

scalar

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16
Q

position

A

location with respect to an origin/comparison point

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17
Q

is position a scalar or vector

A

vector

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18
Q

position is denoted as…

A

s(t)

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19
Q

displacement

A

change in position

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20
Q

is displacement a scalar or vector

A

vector

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21
Q

displacement is denoted as…

A

∆s(t)

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22
Q

center of pressure

A

point of application of that ground force
-all the load being transmitted between that person + the ground is transmitted through the COP

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23
Q

center of pressure trace

A

using a force plate to look at quantitative measures of balance

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24
Q

better balance = looser/tighter COP trace

A

tighter COP trace

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25
Q

velocity

A

change in position over time

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26
Q

velocity is a scalar or vector

A

vector

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27
Q

velocity is the derivative of…

A

position
-velocity = slope of the line tanget to the position function

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28
Q

acceleration

A

change in velocity over time

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29
Q

acceleration is a scalar or vector

A

vector

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30
Q

acceleration is a derivative of…

A

velocity
-acceleration = slope of line tangent to velocity function

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31
Q

acceleration is second derivative of…

A

position

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32
Q

if position curve cups up, acceleration is positive/negative

A

positive
-cups down = negative

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33
Q

inflection point

A

point where curvature of the function goes from curved up to down + vice versa

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34
Q

if position graph is at local min/max, velocity = ?

A

0

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35
Q
A
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36
Q

peak bar velocity

A

-people often use bar velocity to determine the power of their movement
-peak bar velocity is the instant in time when velocity is maximum (instantaneous velocity)

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37
Q

average velocity

A

calculated as a change in displacement over a time interval

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38
Q

instantaneous velocity

A

more discrete measure of velocity measured at a given moment in time
-change in time is infinitesimally small

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39
Q

numerical differentiation

A

computing the slope of the line tangent to a curve for time series data (aka derivative)

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40
Q

what is numerical differentiation used for

A

to calculate instantaneous velocity from discrete time series data

41
Q

central differencing method

A

used to numerically differentiate time series data
-ex: calculating instantaneous velocity at time point 2

42
Q

constant acceleration

A

acceleration is nonzero but constant

43
Q

examples of constant acceleration

A

-projectile motion (batted ball, shotput throw, soccer shot, high jump, diving, human cannonball stunt)
-friction (Olympic sport culing, sliding into home plate, hockey stop)

44
Q

projectile

A

a body in free fall that is subject only to the forces of gravity + air resistance

45
Q

CLASSIC projectile motion

A

object is being projected from the same height that it lands at

46
Q

GENERAL 1 projectile motion

A

object is projected from a height ABOVE where it lands

47
Q

GENERAL 2 projectile motion

A

object is projected from a height BELOW where it lands

48
Q

VERTICAL projectile motion

A

object goes straight up + comes stright back down
-no horizontal aspect

49
Q

HORIZONTAL projectile motion

A

object is projected at 0 degrees off a ledge/cliff
-gains vertical velocity

50
Q

factors that affect projectile motion

A

-projection height
-projection angle
-initial speed

OR

-initial vertical velocity

51
Q

relative projection height

A

the difference between projection height + landing height

52
Q

projection speed

A

magnitude of projection velocity

53
Q

what determines height of trajectory apex of projectile

A

initial vertical velocity

54
Q

what determines horizontal distance covered of a projectile

A

initial horizontal velocity

55
Q

angle of projection

A

the direction at which a body is projected with respect to the horizontal

56
Q

what is determined by angle of projection

A

relative magnitude of vertical vs horizontal components of velocity

57
Q

what will happen to a projectile if it has a large vertical velocity

A

object will fly very high but won’t go very far

58
Q

what will happen if a projectile has equal components of vertical + horizontal velocity

A

longer distance traveled but not as high of an apex achieved
-this is the best option because balance

59
Q

what will happen if a projectile has large horizontal velocity

A

neither a high apex nor long horizontal distance traveled

60
Q

what is the most ideal projection angle (in terms of vertical + horizontal projection angles)

A

equal components of vertical + horizontal velocity

61
Q

CLASSIC SITUATION:
relative height h = ?

A

h = 0

62
Q

CLASSIC SITUATION:
optimum angle

A

45 degrees

63
Q

GENERAL SITUATION:
relative height h = ?

A

h ≠ 0

64
Q

GENERAL SITUATION:
if relative height increases, angle increases/decreases

A

decreases

65
Q

GENERAL SITUATION:
if relative height decreases, angle increases/decreases

A

increases

66
Q

SHOTPUT THROW:
goal

A

maximize horizontal displacement

67
Q

SHOTPUT THROW:
general case

A

height advantage

68
Q

LONG JUMP:
goal

A

maximize horizontal displacement

69
Q

LONG JUMP:
general case

A

technically height advantage because COM is lower when hits ground than at start

70
Q

BASKETBALL FREE THROW SHOT:
goal

A

accurately hit hoop/make basket

71
Q

BASKETBALL FREE THROW SHOT:
general case

A

height deficit

72
Q

consider 2 balls- 1 dropped vertically + 1 projected horizontally from same height:

describe when each hits the ground

A

-both hit the ground at the same time because the vertical + horizontal components are independent of each other
-gravity affects their vertical velocities equally

73
Q

horizontal + vertical components are dependent/independent of each other

A

independent

74
Q

when does horizontal component change

A

only if air resistance is not negligible

75
Q

apex

A

highest point in the trajectory of a projectile
-projectile motion is symmetric on either side of an apex, parabolic

76
Q

describe projectile without air resistance

A

-higher apex
-larger horizontal displacement
-symmetric trajectory

77
Q

describe projectile with air resistance

A

descent of projectile is steeper/asymmetric compared to initial portion

78
Q

acceleration during free fall

A

-9.81 m/s^2

79
Q

which of the following is not a target muscle in the reverse scoop medicine ball throw?

-quadriceps femoris
-anterior deltoid
-gluteus maximum
-gastrocnemius
-trapezius

A

trapezius

80
Q

which is a characteristic of young/active fascia versus older/inactive fascia in terms of its structure

-bidirectional lattice structure
-multidirectional crimp structure

A

bidirectional lattice structure

81
Q

the reverse scoop medicine ball throw strengthens which anatomy train

A

superficial back line

82
Q

which of the following is NOT part of the superficial back line

-plantar fascia
-erector spinae
-gastrocnemius
-latissimus dorsi

A

latissimus dorsi

83
Q

which of the following will stretch the superficial back line?

-seated twist
-standing forward bend
-reverse plank
-bow stretch

A

standing forward bend

84
Q

true/false: the overall movement function of the superfical back line is flexion + twisting

A

false

85
Q

in quantifying the maximum velocity of hand during the pitch motion in softball you are looking to quantify an

-instantaneous velocity
-average velocity

A

instantaneous velocity

86
Q

to make sure you do not miss the time point (or event) you care most about in a movement you should do which of the following

-increase shutter speed
-increase focal length
-increase aperture
-increase frame rate

A

increase frame rate

87
Q

when trying to record movement data in 3D dimensions how many vantages (perspectives) do you need at minimum to percieve all 3 dimensions (x, y, z coordinates) of a marker

A

2

88
Q

true/false: in passive marker based motion capture the markers emit their own light

A

false

89
Q

if an projectile lands ABOVE where it was projected from, describe optimal angle of projection

A

more than 45 degrees

90
Q

if a projectile lands LOWER than projection height, describe optimal angle of projection

A

less than 45 degrees

91
Q

true/false: all else held constant, increasing the horizontal velocity in projectile motion will increase the horizontal displacement but not the flight time

A

true

92
Q

if you have a height advantage, what must you do to optimal angle

A

lower it

93
Q

if you have a height disadvantage, what must you do to optimal angle

A

increase it

94
Q

shoput throw is height advantage/disadvantage

A

height advantage

95
Q

long jump is height advantage/disadvantage

A

height advantage

96
Q

basketball free throw is height advantage/disadvantage

A

height disadvantage

97
Q

what determines flight time

A

-projection height
-projection angle
-initial speed
-initial vertical velocity

98
Q

does initial horizontal velocity affect flight time?

A

no
-partially determines horizontal distance travelled

99
Q

it is easier for the body to generate horizontal/vertical force

A

horizontal

Biomechanics Exam 3 (5 decks)

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