Chapter 7 - Biomechanics Flashcards Preview

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Flashcards in Chapter 7 - Biomechanics Deck (99):
1

what does biomechanics examine?

the internal and external forces acting on the human body and the effects produced by these forces

2

what does biomechanics aid in?

technique analysis and the development of innovative equipment designs

3

where does the knowledge for biomechanics come from?

from sports medicine, athletic therapy, physical therapy, kinesiology and biomechanical engineering

4

Exchange of energy forces

biomechanics

5

quantitative analyses

- involves measurement of variables that are thought to optimize or maximize performance

6

give 3 examples of quantitative analyses

1) pattern of forces using a force platform
2) sequence of muscle activity using electromyography (EMG)
3) 3D movements of each body segment using high speed cinematography

7

qualitative analyses

- involves obtaining information, visually or auditorily to assess performance

8

what 4 things does qualitative analyses require?

1) a framework within which skilled performance can be observed
2) a set of principles with which movement can be analyzed
3) a checklist to use when identifying errors
4) techniques to use for error detection and correction

9

kinematics study of motion

the study of time and pace factors of a body in motion

10

what are the 4 variables used to describe motion?

time, displacement, velocity and acceleration

11

linear

straight line

12

angular

around an axis

13

time

temporal characteristics of a performance, either of the total skill or its phases

14

displacement

length and direction of the path an athlete or object takes from start to finish

15

angular displacement

direction of, and smallest angular change between the rotating bodys initial and final position

16

velocity

displacement per unit of time

17

angular velocity

angular displacement per unit of time

18

acceleration

rate of change of velocity

19

angular acceleration

angular velocity per unit of time

20

kinetics study of forces

focuses on the various forces that are associated with a movement

21

internal forces

generated by muscles pulling via their tendons on bones, and to bone-on-bone forces exerted across joint surfaces

22

external forces

acting from without, such as the force of gravity or the force from any body contact with the ground, environment, sport equipment or opponent

23

scalar quantities

have only magnitude (time)

24

give 3 examples of scalar quantities

speed, work, power

25

vector quantities

have magnitude and direction (force) displacement, velocity, momentum, lift

26

Straight line segments with one end defined as the tail and the arrow tip defined as the head

vectors

27

Levers

simple machines that augment the amount of work done by an applied force

28

fulcrum

a rigid body (i.e., long bone) that rotates about a fixed point (i.e., joint) called a fulcrum (F)

29

true or false: acting on the lever is a resistive force (R, i.e., weight of a limb segment) and applied force (AF, i.e., muscle contraction)

true

30

what are the 3 classes of levers?

a) first class
b) second class
c) third class

31

give an example of a first class lever

teeter-totter

32

give an example of a second class lever

wheelbarrow

33

give an example of a third class lever

barbaque tongs

34

factors affecting the moment of force

a balanced teeter-totter

35

newtons 1st law of motion

the law of inertia

36

the law of inertia

a body will maintain a state of rest or constant velocity unless acted on by an external force that changes the state

37

newtons 2nd law of motion

the law of acceleration

38

the law of acceleration

a force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body's mass

39

newtons 3rd law of motion

the law of reaction

40

the law of reaction

- for every action there is an equal and opposite reaction
- the 2 acting forces are equal in magnitude, but opposite in direction

41

give an example of the law of reaction (newtons 3rd law of motion)

the sprinter exerts a force on to the blocks and simultaneously the blocks exert an equal force back onto the sprinter

42

what is the action and what is the reaction in this example of newtons 3rd law?: the tires on a car push on the road and the road pushes on the tires

action: the tires on a car push on the road

reaction: the road pushes on the tires

43

what is the action and what is the reaction in this example of newtons 3rd law?: while swimming, you push the water backwards and the water pushes you forward

action: while swimming you push the water backwards

reaction: the water pushes you forward

44

what is the action and what is the reaction in this example of newtons 3rd law?: a rocket pushes out exhaust and the exhaust pushes the rocket forward

action: a rocket pushes out exhaust

Reaction: the exhaust pushes the rocket forward

45

why are the models of human motion developed?

because the total movement capacity of all the body structures is to complex to accurately analyze

46

why is the total movement capacity of all the body structures too complex to accurately analyze? (3 reasons)

1) anatomical difference in people related to race, age, gender, health and lifestyle
2) the body is susceptible to deformation and multi-segmental so that one segment affects the others during movement
3) sport skills occur in 3D often encountering all 3 planes and axis

47

what are the 3 human body models?

1) particle model
2) stick figure model
3) rigid segment model

48

particle model

used when the object of interest (the human body or an object) is airborne after being thrown, struck or kicked the body itself (i.e., jumping, diving, tumbling)

49

stick figure model

used when the object is in contact with its environment and generally gross motor skills in 2D (i.e., sprint starts, running, non rotational dive)

50

rigid segment model

used for more sophisticated quantitative analyses (3D) especially in multi-plane motions

51

what 2 things are required for rigid segment model?

camera and 3D analysis

52

what is the first preliminary step for analyzing human motion?

identify the system to be studied, which is to separate the object of interest from its surroundings

53

what is the second preliminary step for analyzing human motion?

identify the frame of reference in which the movement takes place

54

what is the third preliminary step for analyzing human motion?

identify the type of motion that is occurring, the body planes in which movement takes place (sagittal, frontal or transverse and
identify the axes of rotation about which rotational motion occurs (sagittal, frontal, or vertical)

55

what are the 3 types o motion?

linear, general and angular

56

motion

when all parts of the body move the same distance in the same direction at the same time

57

linear motion (AKA translation)

refers to movement of the body as a unit without individual segment parts of the body moving relative to one another

58

rectilinear motion

occurs when movement follows a straight line

59

curvilinear motion

occurs when the movement path is curved

60

angular motion (rotation)

occurs when a body moves along a circular path, through the same angle in the same direction and at the same time

61

what is the point about which movement occurs?

the axis of rotation

62

all joints are what type of motions?

angular motions

63

general motion

a combination of linear and angular motion

64

what does general motion include?

most athletic and many everyday activities

65

causes of motion

the only cause of motion of the human body is the application of an external force

66

force

any action, a push or pull, which tends to cause an object to change its state of motion by experiencing an acceleration

67

constant velocity

occurs when an object is not accelerating

68

linear motion

is caused by forces which act through a body's centre of mass

69

angular motion

caused by forces that do not go through the centre of mass

70

centre of mass

located at the balance point of a body; a point found in or about a body where the mass could be concentrated

71

where is the centre of mass generally?

generally 15cm (approx. 6inches) above the symphysis pubis, or approx. 55% of standing height in females and 57% in males

72

does the centre of mass have to be inside the body?

no

73

mass

a measure of inertia a constant what object is made up of

74

what is mass measured in?

kilograms

75

weight

measure of the force of gravity

76

what is weight measured in?

newtons

77

what makes the weight vary?

varies directly with the magnitude of the acceleration due to gravity (9.8m/s2)

78

Weight = _____ x ______

mass x gravity

79

Projectile Motion

any airborne object is a projectile, including the human body

80

parabolic path

the path that the centre of mass of a projectile follows

81

what is the parabolic path followed determined as?

determined only as a function of the projectiles takeoff velocity

82

what are the objectives of the projectile motion (what do you want the object to do)?

height - max vertical distance
range - max horizontal distance
accuracy

83

what is the optimum trajectory for distance?

35 degrees

84

what is the first principle?

stability

85

stability increases when there is...?


- a lower centre of gravity
- an increase in the base of support
- the line of gravity is close to the centre of the base of support
- mass increases

86

what is principle #2?

maximum force

87

how is maximum force achieved

by the use of all the joints that can be applied simultaneously

88

more joints = more ______ = more _______

more joints = more muscles = more force

89

what is the third principle?

maximum velocity

90

how is maximum velocity achieved?

when the joints are sequences from largest to smallest

larger slower joints start the movement, faster smaller joints contribute once the preceding joint reaches peak velocity and slow down

91

what is principle #4?

Impulse

92

the greater the applied impulse the greater the _______

the greater the applied impulse the greater the change in velocity

93

when does force absorption occur?

when momentum must be dissipated over time or distance (requires application of an impulse)

94

what is the fifth principle?

linear motion

95

movement usually occurs in the direction opposite that of the _______ force

movement usually occurs in the direction opposite that of the applied force

96

what is principle #6?

Angular Motion

97

how is angular motion produced

angular motion is produced by the application of a force acting at some distance from an axis, that is, by a torque

98

what is the seventh principle?

angular momentum

99

angular momentum is _____ when an athlete or object is free in the air (i.e., constant after takeoff)

angular momentum is constant when an athlete or object is free in the air (i.e., constant after takeoff)