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Biomechanics > Intro / Linear Kinematics > Flashcards

Intro / Linear Kinematics Flashcards

1
Q

what is biomechanics?

A

study of forces and their effects on living systems

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2
Q

statics

A

mechanics of objects at rest or in uniform motion

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3
Q

uniform motion

A

constant velocity, > 0m/s
acceleration is zero

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4
Q

dynamics

A

mechanics of objects in accelerated motion

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5
Q

kinematics

A

description of motion independent of the cause (what we observe)

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6
Q

kinetics

A

forces that cause or change motion

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7
Q

sagittal plane

A

vertical and AP axis

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8
Q

frontal plane

A

vertical and ML axis

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9
Q

transverse plane

A

AP axis and ML axis

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10
Q

linear motion (translation)

A

along an axis

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11
Q

angular motion (rotational)

A
  • around an axis
  • fixed axis
  • paths different lengths
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12
Q

plane

A

a 2D surface defined by 3 points not on the same line (not colinear)

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13
Q

motion

A

process in change in position over time

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14
Q

rectilinear motion (rare)

A

motion along a straight line or path

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15
Q

curvilinear motion (common)

A
  • motion along a curved line or path
  • no fixed axis
  • paths same length
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16
Q

examples of angular motion

A

leg raises (internal axis)
swinging from a bar (external axis)

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17
Q

qualitative kinematic analysis

A

visual observation of motion

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18
Q

quantitative kinematic analysis

A

measurement

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19
Q

most commonly used spatial reference system

A

Cartesian coordinate system

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20
Q

global coordinate systems

A

1D, 2D, 3D

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21
Q

local coordinate systems

A

relative angle & absolute angle

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22
Q

relative angle (joint angle)

A

local CS relative to another local CS

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23
Q

absolute angle (segment angle)

A

global GS relative to a local CS

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24
Q

scalar

A

magnitude only

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25
Q

vector

A

magnitude & direction

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26
Q

linear position

A
  • location in space
  • avg or instananeous
  • ref point needed
27
Q

example of linear position

A

shuttle run (no displacement)

28
Q

distance (l)

A
  • length of the path of motion
  • scalar
29
Q

displacement (d or delta s)

A
  • change in position in a specific direction
  • vector
30
Q

displacement equation

A

Δs = s final - s initial

31
Q

use of distance in gait analysis

A

left side stroke, shorter right step

32
Q

what is a runner’s displacement if they compete:

a) one lap
b) ten laps
c) 1/2 lap

A

a) 0 m
b) 0 m
c) 200 m

33
Q

calculating linear displacement with two coordinates

A

1) Δy = yf - yi, Δx = xf - xi

2) d = √Δx^2 + Δy^2

34
Q

calculating direction (angle of resultant)

A

SOH CAH TOA

35
Q

speed

A
  • how fast a person or object is moving
  • scalar
36
Q

speed equation

A

speed = distance / time

37
Q

velocity

A
  • how fast a person or object is moving in a specific direction
  • vector
38
Q

velocity equation

A

velocity = displacement / change in time (Δposition / Δtime)

39
Q

What is the resultant velocity if it tok a hiker 13 hrs and 45 min to hike from Yosemite National Park to Lake Tahoe?

Map: 77 miles 60 degrees N of W = resultant displacement

A

1) convert miles to m and time to sec

2) v = Δposition / Δ time

v = 123919 m / 49500 sec
v = 2.5 m/s, 60 degrees N of W

3) direction: break into x and y components

y-component = 2.5sin60 = 2.17 m/s N
x-component = 2.5cos60 = -1.25 m/s W

40
Q

T/F: a change in the body’s velocity may represent a change in its speed, movement direction, or both

A

True

41
Q

example of linear speed

A

gait speed

42
Q

gait speed

A

stride length x stride frequency

increasing one or the other increases gait speed

43
Q

A runner completes 6 1/2 laps around a 400 m track that has a diameter of 160 m. It takes the runner 12 min (720 s) to complete the run. Calculate the following:

a) distance covered
b) displacement at the end of 12 min
c) average speed
d) average velocity

A

a) 2600 m
b) -160 m or 160 m south
c) 3.61 m/s
d) -0.22 m/s

44
Q

most economical runner

A

lowest submaximal oxygen consumption (VO2)

45
Q

most economical trunk angle

A

greater trunk lean (5.9)

46
Q

most economical max. knee flexion in support

A

greater knee flexion (43.1)

47
Q

most economical wrist excursion

A
  • medium wrist excursion (80.7)
  • “goldilocks zone”
48
Q

most economical vertical oscillation

A

lower levels of vertical oscillation (9.1)

49
Q

Brian is trying to swim in the ocean from west to east at a velocity of 1.5 m/s. However, the water current is pushing him at an angle of 20 degrees west of south at a velocity of 0.5 m/s. What is Brian’s resultant velocity?

A

1) break into x and y components
2) SOH CAH TOA
3) sum x components and y components separately
4) plug into resultant velocity equation

Vr = 1/41 m/s
θ = 70.53 degrees east of south

50
Q

linear acceleration

A

the change in motion of an object

51
Q
A
52
Q

acceleration equation

A

acceleration = change in velocity / change in time (Δv / Δt)

53
Q

EXAM: acceleration may be positive, negative, or zero, based on:

A
  • direction of motion
  • change in velocity (slowing down, speeding up)
54
Q

case 1: speeding up in the positive direction

A

+ velocity
speeding up
+ acceleration

(+)(+) = (+)

55
Q

case 2: slowing down in the positive direction

A

+ velocity
slowing down
- acceleration

(+)(-) = (-)

56
Q

case 3: speeding up in the negative direction

A
  • velocity
    speeding up
  • acceleration

(-)(+) = (-)

57
Q

case 4: slowing down in the negative direction

A
  • velocity
    slowing down
    + acceleration

(-)(-) = (+)

58
Q

If a runner is slowing down in the positive direction: what is acceleration?

A

negative

(+)(-) = (?)

58
Q

A runner’s final velocity is positive: Running in the positive direction. Acceleration is negative. Is the runner speeding up or slowing down?

A

slowing down

(+)(?) = (-)

59
Q

+ velocity, + acceleration

A

speed is increasing (speeding up)

60
Q
  • velocity, - acceleration
A

speed is decreasing (slowing down)

61
Q

Andrea is running at a speed of 3.0 m/s in the negative direction at time 4 s. Her acceleration between time 4 s and 6 s was -2.5 m/s^2. Was she slowing down or speeding up?

A

speeding up

(-)(?) = (-)

or

a = Δv / Δt
solve for vf

62
Q

to be able to identify sign (direction of acceleration, need to know:

A
  • direction of motion (sign of velocity)
  • if v is increasing or decreasing (speeding up/slowing down)
63
Q

to be able to identify if person/object is speeding up/slowing down, need to know:

A
  • direction of motion (sign of velocity)
  • sign of acceleration

Biomechanics (3 decks)

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