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
