Chapter 7 - Biomechanics Flashcards Preview

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Flashcards in Chapter 7 - Biomechanics Deck (99)
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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