Lec 15-18 Flashcards
1
Q
How does the contact point of a system change the movement?
A
the further you are from the middle (centre of mass), the more rotation you can get, with less translation
2
Q
How would pushing from the centre or middle of an object affect its translation
A
it would increase its translation, or make it easier
3
Q
how would pushing an object further from its centre change its rotation
A
it would make rotation easier, so there is more of it
4
Q
how would pushing an object further from the middle affect its translation
A
it would result in less translation
5
Q
how would pushing an object at its centre affect its rotation
A
it would result in less rotation
6
Q
define centre of gravity
A
centre of gravity: the point around which a system’s weight is equally distributed in all directions
7
Q
what is another word for centre of gravity
A
centre of mass
8
Q
how is centre of mass and centre of gravity different?
A
refers to the same spot, but reference a different quantity. Centre of gravity discusses forces whereas centre of mass only looks at mass concentration
9
Q
what determines how a body will respond to external forces
A
The location of centre of gravity
10
Q
how can we located the centre of gravity on an animate object?
A
It depends on the situation. The centre of gravity can change with animated bodies, since movement changes the distribution of masses
11
Q
how does movement result in a change of location of the centre of gravity
A
with animated objects, movement changes the distribution of masses. It can be inside or outside of you based on your position in space
12
Q
where is the centre of gravity typically located on a person?
A
typically it sits right above the belly button, roughly 55% of height
13
Q
in what scenario would our centre of gravity be outside of the body
A
If you are bent over
14
Q
in what scenario would our centre of gravity be sitting right above our belly button
A
if we are in an upright, relaxed positionin
15
Q
in what scenario would our centre of gravity be higher than our belly button
A
If we are stretching upwards (while standing)
16
Q
How do we measure the centre of gravity
A
- force platforms
- balance procedure
17
Q
how do we use force platforms to measure the centre of gravity
A
Force plates allow us to measure the forces of gravity in different scenarios of standing upright/leaning etc.
18
Q
how do balance procedures help us measure the centre of gravity
A
We use a wooden board to locate the position where it is balanced
19
Q
What is a centric force
A
centric force: the force that is directed towards the centre of gravity
20
Q
When a force acts directly at the centre of gravity, it will produce _____ only
A
translation
21
Q
when a force acts away from the centre of gravity, it will produce _______
A
translation AND rotation
22
Q
define a pure moment
A
pure moment: occurs when two forces equal in magnitude but opposite in direction act equidistant from the centre of gravity
23
Q
when a centric force acts directly on the centre of gravity, it will produce ____
A
translation only
24
Q
Define eccentric force
A
eccentric force: a force that acts away from the centre of gravity
25
when an eccentric force acts away from the centre of gravity, it will produce ______
translation and rotation
26
what force produces rectilinear motion only
centric force
27
what does moment mean?
rotation. so a pure moment is going to be one where the two forces of equal magnitude but opposite direction will turn the object in the same direction
28
what force produces curvilinear motion only
eccentric force
29
what does a pure moment result in? (movement wise)
rotation. NO translation
30
what is a couple of forces?
couple: two eccentric forces that cause rotation only
31
what is the name for two eccentric forces that cause rotation only
couple
32
do couples produce a net force?
no. there is no net force.
33
what is the name for a force that acts directly on a centre of gravity
centric force
34
what is the name for a force that acts off-centre from the centre of gravity
eccentric force
35
a force applied away from an anchor point will do what?
rotate
36
what is the anchor point
anchor point is the axis of rotation, AKA fulcrum AKA pivot point
37
what is the fulcrum
the pivot point = anchor point = axis of rotation
38
how can a linear force create angular rotation?
A linear force can cause angular rotation if there is a fixed point, or anchor point
39
Define torque
torque: a force that has a tendency to rotate an object about an axis
40
what is another word for a rotational force
torque
41
what is another word for a moment of force, or moment?
rotation, aka torque
42
What factors does torque depend on
1. magnitude of force
2. point of application
3. direction of force
43
what is the formula for torque
torque = force x moment arm
44
what is a moment arm
moment arm: the perpendicular distance between the line of action of the force and the axis of rotation
45
what are the units for torque
Nm
46
How do we use the direction of force to calculate torque
Force have horizontal and vertical components, but only one of these will have an impact. this is the one that is directly perpendicular
47
how do we find the movement arm?
from the axis of rotation, or pivot point, we draw a line to the force arrow so that it meets at a 90 degree angle. this line that we drew is the moment arm
48
how is torque used with doors?
door handles are placed furthest away from the hinge, or fulcrum. this is so that the least amount of force is needed for movement
49
what is a lever
lever: a relatively rigid object that may be made to rotate about an axis by the application of a force
50
what do levers do?
they magnify the effect of a muscle
51
What are the types of levers?
1. first class
2. second class
3. third class
52
how do we classify different types of levers?
classified by the relative positions of the forces to the axis of rotation
53
what are the components of all levers
- the rigid body: the system being moved
- the fulcrum: the axis of rotation or pivot point
- the effort: the input force or the applied force
- the resistance: the output force
54
what determines the effectiveness of a lever?
mechanical advantage
55
what is the mechanical advantage?
mechanical advantage: the ratio of the output force to the input force
56
how do we measure mechanical advantage
we measure the distances between the forces to the axis of rotation
57
In what scenario can a force balance a larger resistance?
when the force arm is longer than the resistance arm
58
as mechanical advantage increases, what happens to speed and strength of a lever?
speed decreases while strength increases
59
as mechanical advantage decreases, what happens to the lever speed and strength?
speed and ROM increases, but strength decreases
60
what is a first class lever
first class lever: a lever that has the fulcrum in the middle of the lever, with effort and resistance on either side/end of the lever
61
what is a second class lever
second class lever: type of lever that has the fulcrum off to one side of the lever, with resistance in the middle and effort on the end
62
what is a third class lever
third class lever: a type of lever that has the fulcrum on the side, with effort in the middle and resistance on the end.
63
what type of lever has a mechanical advantage less than 1?
third class lever
64
what type of lever has a mechanical advantage greater than 1
second class lever
65
what type of lever has a mechanical advantage greater/less than 1
first class lever
66
most muscles in the body are what kind of lever?
third class
67
why are most muscles third class levers?
because it amplifies the speed and ROM
68
what are the types of angular motion
1. yaw
2. pitch
3. roll
69
define yaw
yaw: the rotation to the left or right
70
what axis does yaw rotate around
vertical axis
71
what is pitch
pitch: rotating up or down
72
what axis does pitch rotate around
mediolateral axis
73
what is roll
roll: tilting to the left or right
74
what axis does roll rotate around
anterioposterior axis
75
how are translation and angular motion different in their fixed points?
translation does not have a fixed point, but angular motion does
76
what is an external axis of rotation
external axis of rotation: it is a point of rotation (i think) outside of the body, where the system moves in a circular path
77
what is an internal axis of rotation
internal axis of rotation: it is a point of rotation inside of the body, where the system moves in a circular path around the axis
78
what is the anatomic reference position
anatomic reference position: the standard reference position for the body when we describe locations, positions or movements of the body
79
Describe the position of the body in the anatomical reference position
palms forward, fingers extended, arms straight by the side, facing forward, body erect, toes forward and feet aligned
80
what are the different cardinal planes
1. saggital
2. frontal
3. transverse
81
describe the saggital plane. what does it split down the middle?
left and right
82
describe the transverse plane. what does it split down the middle?
top and bottom
83
describe the frontal plane. what does it split down the middle?
front and back
84
how do we analyze motion?
we use video motion analysis
85
what is video motion analysis
video motion analysis: a method of analyzing motion that utilizes cameras and reflective markers to produce a 3D model
86
how does video motion analysis work?
we use reflective markers on the body, camera and computer to generate a 3D model of the body and its corresponding movement
87
what does video motion analysis measure
change in position, speed of motion, change in the state of motion
88
what do we use video motion analysis for in a clinical/real life sense
gait analysis, sport replays, measure performance
89
what is an angle
angle: the space between two intersecting lines or surfaces, at or close to their intersection
90
what are the types of angles?
1. relative angle (internal and external)
2. absolute angle
91
define relative angle
relative angle: the space between the longitudinal axes of adjacent segments
92
what are the components of a relative angle?
1. internal relative angle
2. external relative angle
93
define absolute angle
absolute angle: the space between a body segment with respect to a fixed line of reference
94
how many lines are needed for relative vs absolute angles?
relative needs two, absolute only needs one!
95
Which is better, relative or absolute angles?
It depends on the situation! It doesn't really matter either way
96
What do we need to identify an angle?
we need to know the location of three joint centres of rotation, including the origin of motion. this allows you to create two longitudinal segments from these three points
97
How many joint centres and longitudinal segments do we need to identify an angle
3 joint centres, and 2 longitudinal segments
98
define degree
degree: a common measure of angles, ranging from 0 to 360 degrees. ARBITARY!
99
define revolution
revolution: a simple and natural measurement for one full turn around a circle. RELATIVE
100
define radian
radian: represents the relationship between the length of a line and the angle you find, AKA the relationship between the arc length and the radius. UNITLESS
101
How do we find a radian on a circle?
draw three lines, of equal length, two from the point of the circle to the outside, and one connecting the two along the circumference. the angle between these is 57.3 degrees, or one radian
102
what was invented in the 1700s by mathematicians who wanted to define angles in a rational way?
radians
103
which of these is the standard unit of measure for angular variables when measuring human movement?
all of them!! sometimes the units have to be in a certain form, though
104
how many revolutions in 360 degrees
one
105
what is the conversion of revolutions to radians
revolution = 2 pi radian
106
what is the conversion of radian to degrees
2 pi radian = 360 degrees
107
what is the conversion of degrees to one radian
57.3 degrees = 1 radian
108
if a wheel rotates around 7.25 revolutions, how many radians did it complete?
1 rev = 2 pi radian
7.25 rev = 7.25 (2pi radian)
7.25rev = 45.5 radian
109
what instrument do we use to measure angles?
goniometer: an instrument that measures an angle
110
what are the types of goniometers?
1. basic goniometer: measures angles in pictures, best for static analysis
2. electrogoniometer: measures angles during movement, best for dynamic analysis
111
what type of goniometer should we use for static analysis?
basic goniometer
112
what type of goniometer should be used for dynamic analysis?
electrogoniometer
113
what is an example of an axis of rotation in a fixed position
a door that rotates around a hinge
114
what is an example of an axis of rotation that is not fixed? what happens as a result?
example idk - the longitudinal segment will shift position as the axis migrates
115
How do we describe an object's position in space?
- angular distance
- rotation amount (scalar)
- units: degrees, revolutions and radians
116
how do we describe temporal patterns of angular movement?
- angular speed
- angular velocity
- angular acceleration
117
what is a temporal pattern of movement
temporal pattern of movement refers to the timing or rhythm of a movement
118
what is angular velocity
angular velocity: the change in angular displacement over change in time. it is produced by torque, and is involved in dynamic motion
119
what is angular acceleration
change in angular velocity/change in time
120
what is the angular acceleration of the second hand on a clock after one complete revolution
0, since velocity is 0 then so is acceleration
121
what do the signs in front of angular displacement/velocity tell us about movement?
plus sign = counterclockwise movement, to the right
negative sign = clockwise movement, to the left
122
what sign do we use for clockwise movement
negative
123
what sign do we use for angular movement to the left
negative
124
what sign do we use for counterclockwise angular movement
positive sign
125
what sign do we use for angular movement to the right
positive
126
what does the sign of movement reflect with torque?
The sign of velocity does not tell us anything, but the sign of acceleration does. if acceleration is -, we know that torque is acting in opposition to the applied force. if acceleration is +, we know that torque is acting in the same direction as the applied force
127
what happens to angular velocity if torque and movement go in the same direction
velocity increases
128
what happens to angular velocity when torque and movement are going in opposing directions
velocity decreases
129
what kind of movements occur in the saggital plane
flexion/extension and hyperextension
130
what movements occur in the anterioposterior axis
abduction and adduction, elevation and depression, lateral flexion and roll
131
what movements occur in the longitudinal axis
medial rotation and lateral rotation, yaw
132
how do angular changes equate to linear changes in an attempt to do general kinematics or general motion?
in running, we can analyze both the rotation of the hip joints or shoulders, while looking at the translation of the limbs at the legs or arms
133
describe the angular and linear motion of a ball as it spins through the air
the ball spins (rotates) as it travels through the air (translation)
134
Is a change in linear position on a rotating object different along the systems' points
yes! the linear change will be different at each point of a system, dependent on the distance between the axis and point of interest
135
what does l_t = r Φ represent
how far a point on that system translates (tangential displacement?)
136
what does ω mean
ω = angular velocity
137
what does v_t = r ω represent
tangential velocity
138
what does Φ mean
Φ = angular distance
139
What does a = r (alpha) represent?
the size of the dynamic change, aka acceleration
140
what angular measurement is arbitrary?
radius of rotation - since you can choose any interest point for the radius
141
Explain why we use scalar and vector quantities in angular questions
because of the radian. The radian is the relationship between arc line and radius, so if we measured displacement instead of the arc line, we would be losing out on a lot of distance covered. (think of the diagram that I have in the word doc, where cutting across the circle leaves out all the distance in red. rotation involves the magnitude of the change and its direction
142
define radius of rotation
radius of rotation: the linear distance from the axis of rotation to a point of interest on the system
143
what kind of a measurement is radius of rotation? linear or radians?
linear! All we are doing with the radius of rotation is measuring two points of interest
144
why do batters "choke up"? what is the biomechanical advantage
choking up = sliding hands away from the bottom of the bat, allowing for more precision/control but less speed.
145
what does choking up do for speed and control
choking up = decreased speed; increased control
146
what does choking down do for speed and control
choking down = increased speed; decreased control
147
if a ball spins in a clockwise direction, when the ball is placed on the ground, the angular motion will create linear movement. which way will the ball translate? to the left or to the right?
to the right!
148
Define tangent
tangent: a line that touches but never crosses...
149
what is another word for tangential
linear
150
what is the formula for tangential velocity
v_t = r ω
151
can an object moving around a curve at a constant speed be accelerating?
Yes! Linear velocity throughout the entire movement will seem to be constant, but your direction is changing as you move around a curve. therefore velocity will be of the same magnitude but of different signs and values, so it is changing.
152
when is centripetal acceleration present
when an object changes direction
153
centripetal acceleration occurs from a force directed at what?
the axis of rotation
154
what is the formula for centripetal acceleration
a_r = v^2/r
155
What does centripetal acceleration reflect?
how fast you are going or how sharp of a turn you are making
156
As radius of rotation decreases, what happens to centripetal acceleration (a_r)
centripetal acceleration increases
157
as velocity increases, what happens to centripetal acceleration (a_r)
a_r increases
158
as velocity decreases, what happens to centripetal acceleration
a_r decreases
159
as radius of rotation increases, what happens to centripetal acceleration
a_r decreases
160
If you are running track, which lane do you want? consider from a biomechanical perspective, psychological perspective and a mix of both
biomechanical = lane 8, since it results in the longest turn (least sharo)
psychological = lane 1, since you can see everyone ahead of you and know how hard you have to push
mix of both = lane 4, since it combines biomechanical and psychological
161
a tighter turn requires more ____
force
162
the total acceleration of a system is the vector sum of what?
the tangential acceleration and centripetal acceleration *look at graph in notes*
163
the total acceleration of a system in centripetal/rotational motion is what
the sum of tangential acceleration and centripetal acceleration
164
what is the equation for the total acceleration of a system in rotation/centripetal motion
total acceleration = square root [(centripetal acceleration)^2 + (tangential acceleration)^2]
165
What does stretching do for the body
increases our range of motion, AKA angular displacement
166
how does range of motion affect performance?
it improves it, by affecting both linear and angular motion
167
What is the relationship between linear and angular variables in external general motion, positive, logarithmic, negative etc.
positive linear - if linear variables increase, so do angular variables. this is NOT the case with internal movements
168
What is the relationship between linear and angular variables in internal general motion, positive, logarithmic, negative etc.
non-linear.
169
linear changes at the muscle result in what changes at the joint?
angular changes
170
what changes in muscle result in angular changes at the joint
linear muscle changes.
171
What do we mean by "dynamic change"? What vector measurement represents this?
acceleration! It refers to the change in velocity, AKA dynamic movement.
172
What axis does medial/lateral rotation and yaw occur in?
Longitudinal (vertical) axis
173
What axis does abduction/adduction, elevation and depression, lateral flexion and roll occur in
Anteroposterior axis
174
What plane does flexion, extension and hyperextension occur in
Saggital plane
175
What axis does flexion occur in
Anteroposterior axis
176
What axis corresponds to the saggital plane
Frontal/mediolateral axis
177
What axis corresponds with the frontal plane
Sagital/anterioposterior axis
178
What axis corresponds with the transverse plane
Vertical/longitudinal
179
What plane corresponds to the frontal/mediolateral axis
Sagittal plane
180
What plane corresponds to the sagittal/anterioposterior axis
Frontal plane
181
What plane corresponds to the longitudinal/vertical axis
Transverse plane
182
what units are arbitrary
degrees
183
what measurement/movement is relative
rotation
