Exam 2 Flashcards
1
Q
definition: forces that cause motion or are caused by motion
A
linear kinetics
2
Q
example of linear kinetics
A
gravity, impact force,
3
Q
Newtons laws: the basis of ______
A
mechanics
4
Q
What is newtons first law of motion
A
the law of inertia: the body in motion stays in motion or at rest stays at rest unless acted on by an outside force
5
Q
definition: the quantity of motion a body possesses (body must be moving)
A
momentum
6
Q
what is the equation for momentum?
A
M = m x v
7
Q
how does momentum change?
A
by changing mass or velocity
8
Q
in absence of _____ ______, the total momentum of a given system remains constant
A
external forces
9
Q
definition: objects in a head on collision bounce off each other. combined momentum is conserved
A
elastic collision
10
Q
definition: objects in the collision stay together after the collision and move together with the same velocity. combined momentum is also conserved
A
inelastic (plastic) collision
11
Q
what is Newtons second law?
A
law of acceleration: force applied to a body causes 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
12
Q
what is the equation for newtons 2nd law of motion
A
F = m x a force = mass x acceleration
13
Q
impulse is the product of _____ times ____
A
force times time
14
Q
if an impulse acts on a system, it will change the ______ _____ of the system.
A
total momentum
15
Q
landing in a relaxed rather than rigid manner allows reduction in ___ ____ on the joints by dissipating _____ over a long period of time.
A
impact forces; force
16
Q
in impulse equations, what must mass be in ?
A
Kg
17
Q
what is newtons third law?
A
law of action-reaction: for every action there is an equal and opposite reaction
18
Q
what is an example of newtons 3rd law?
A
ground reaction force
19
Q
when one body exerts a force on a second, the second body exerts a _____ force that is _____ in magnitude and _____ in direction to the first body
A
reaction; equal; opposite
20
Q
What is a common force we can use to our advantage?
A
Ground reaction force
21
Q
Jumpers use ground reaction force to convert ______ velocity to ______ velocity
A
horizontal to vertical
22
Q
runners can experience _____ due to GRF
A
injuries
23
Q
GRF & ______ data can determine the amount of _____ at each joint
A
kinematic; force
24
Q
when running, each time your foot hits the ground, ____ x your body weight is exerted through your lower extremity
A
2 - 3 x
25
force pattern varies with running \_\_\_\_\_
style
26
GRF can be measured by a
force palate (precise scale that measures forces in 3 dimensions -- x,y,z)
27
4 factors influencing GRF
1. running speed 2. footwear 3. ground surface 4. grade of surface
28
(Newtons Law of \_\_\_\_\_\_) All bodies are attracted to one another with a force _______ to the product of their masses and _____ to the distance between them.
gravitation; proportional; inversely
29
definition: collision of two bodies in a small amount of time
impact
30
3 types of impact
1. perfectly elastic 2. perfectly plastic 3. somewhere in between
31
what type of impact: the velocities of the 2 bodies remain equal before and after impact. example?
perfectly elastic. ball bouncing
32
what type of impact: at least one body deforms and does not regain its original shape and bodies do not separate. Example?
perfectly plastic. car crash
33
definition: a unit-less number between 0 and 1 that is used to describe the relative elasticity of an impact
coefficient of restitution
34
what does the number 1 represent ? the number 0 ?
1 = perfectly elastic 0 = perfectly plastic
35
when two bodies undergo a direct \_\_\_\_\_\_, the difference in their velocities immediately after an impact is _____ to the difference in their velocities immediately before impact.
collision; proportional
36
what does Hb stand for? Hd?
Hb = bounce height Hd = drop height
37
What unit does the coefficient of restitution use?
none. it's a unit less number
38
work is the produce of _____ and _______ (distance)
force and displacement
39
what is the equation for work?
U = fd
40
definition: the object is moved in the same direction of the force
positive work
41
definition: the object is moved in the opposite direction of the force
negative work
42
what type of work do eccentric and concentric muscle contractions do?
concentric = positive work eccentric = negative
43
definition: rate of mechanical work
power
44
what unit is used to represent power?
watt
45
capacity of a body to do work
mechanical energy
46
3 types of mechanical energy
1. kinetic 2. potential 3. strain
47
energy in motion
kinetic energy
48
energy due to position
potential energy
49
KE = ?
1/2 mv squared
50
PE = ?
weight x height OR mass x height x gravity
51
energy of elasticity stored energy in the deformation of an object
strain energy
52
example of strain energy?
pole vault pole, tendons
53
Strain energy (SE) = ?
1/2 kx squared k = stiffness, x = length
54
when gravity is the only acting external force, a body's mechanical energy remains \_\_\_\_\_\_
constant (law of conservation of energy)
55
the work of a force is equal to the change in energy that it produces in the object acted on it
principle of work and energy
56
what is the equation for conservation of energy?
1/2mv squared = mgh (KE equation = PE equation)
57
torque is a moment of \_\_\_\_\_
force
58
torque is a _____ effect created by an applied force
rotary
59
torque is the ______ equivalent of linear force
angular
60
what is the equation for torque with a 90 degree angle?
T = F x r
61
a force applied through a body's ______ of rotation results in linear motion or no motion depending on the _____ of force applied
center; amount
62
greater torque results in a greater tendency for _____ to occur and a greater angular \_\_\_\_\_\_\_
rotation; acceleration
63
definition: perpendicular and shortest distance between a force's line of action and axis of rotation
moment arm
64
any deviation from the _______ will change the moment arm length
perpendicular
65
definition: pair of equal and opposite forces that produce torque in the same direction
force couple
66
in a force couple, both have equal \_\_\_\_\_\_, and even though they're on opposite sides of the axis of rotation, their effects on the body are _____ together
magnitude, added
67
counterclockwise rotation is \_\_\_\_\_\_; clockwise rotation is \_\_\_\_\_\_\_
positive; negative
68
when examining the direction of joint rotation, what two things are important?
1. position of the body 2. position of the person observing the movement (could be clockwise or counterclockwise depending on stance)
69
Joint torques produce movement of _____ \_\_\_\_\_
body segments
70
Muscles (through \_\_\_\_) pull on points across a center of rotation (\_\_\_\_\_), thus creating \_\_\_\_\_\_\_
tendons, joints, torques
71
agonistic and antagonistic muscles are working so the change in joint position is a result of ____ \_\_\_\_\_
net torque (whichever is greater produces net torque)
72
what 5 things are joint torques influenced by ?
1. segment weight 2. segment motion 3. segment length 4. external motion 5. external forces (weight, pulley system, etc.)
73
what is the equation for torque when the angle is other than 90 degrees?
Fc = rF x sin0
74
\_\_\_\_\_ torques can be measured directly or indirectly
joint
75
to measure joint torques directly, place a strain gauge in the \_\_\_\_\_\_
muscle
76
how could you measure joint torques indirectly?
Electromyography (EMG) Isokinetic device
77
what does indirect measuring, measure?
torque, segment motion (used in physical rehabilitation and for bilateral comparison)
78
definition: a rigid bar rotating around about an axis or fulcrum
levers
79
a bone is an example of a ____ and a joint is an example of a \_\_\_\_\_
bar; fulcrum
80
the force applied by levers will move a \_\_\_\_\_\_
resistance
81
three types of levers
first second third class levers
82
example of first class lever, and one example in the body
- see saw - triceps
83
example of second class lever & one example in the body
- wheelbarrow - calf-muscle
84
example of third class lever & one in the body
- broom - biceps
85
which lever is the most common in the body?
third class levers
86
WHAT CLASS lever is this
87
what class lever is this?
88
what class lever is this
89
2 purposes of levers
1. gain mechanical advantage
2. gain a greater range of motion
90
If a moment are of force is longer than the moment arm of resistance, the magnitude or the applied force neede to move a given resistance is less than the magnitude of the resistance. What lever is an example of this?
Second class lever. (few muscles are set up this way, but calf muscles are; wheelbarrow)
91
If the resistance arm is longer than the force arm, the resistance may be moved through a relatively large distance. What is this an example of?
3rd class levers; most joints in our bodies
92
mechanical advantage = ?
moment arm force / moment arm resistance
93
if the mechanical advantage value is:
\> 1, \< 1 or = 1
\> 1 (gain mechanical advantage)
\< 1 (lose mechanical advantage)
= 1 (no mechanical advantage)
94
if the value is \> 1, the force required is ____ than the resistance
less
95
if the value is \< 1 the force required is _____ than resistance
greater
96
most levers in the human body are ____ class and their mechanical advantage is ___ 1.
3rd class; \< 1
97
in the human body lever rom and speed are \_\_\_\_\_\_
emphasized
98
for joint movement to occur in the body muscle frces generated must be in _____ of ______ forces
in excess of resistance forces
99
definition: the only force component that will cause the bone to rotate around the joint center.
rotary component
100
the rotary component is ______ to the bone and is known as the __ component
perpendicular; y component
101
definition: the component of the force parallel to the bone, pulling the bone away from the joint center
dislocating component
102
definition: the component of force that is parallel to the bone, pulling the bone toward the joint center
stabilizing component
103
both of the dislocating component and the stabilizing component can be part of the __ component
x
104
whent a lever has an angle \< 90 degrees, it has both a rotary (y) component and a ______ (x) component
dislocating (since its pulling it away from the joint center
105
when the lever has an angle \> 90 degrees, it has both a rotary (y) component and a ______ (x) component
stabilizing (bc its pulling toward joint center)
106
when the lever has a 90 degree angle, is has a 100% ____ component
rotary component; 100% of the force of the tendon causes rotation
107
as we move a joint through its range of motion, the muscle that is moving the joint is _____ and more _____ at different joint angles
stronger; stable
108
the specific joint _____ in which the muscle is stronger/stable ____ from person to person and joint to joint
angles; varies
109
angles are in reference to the _____ compared to the bone and not bone compared to bone
muscle
110
the position of the muscle relative to the bone will change the joint \_\_\_\_
angle
111
force generated (strength) during elbow flexion is highest at __ degrees (joint angle)
80
112
the _______ of the muscle determines the force generated
length
113
look at muscle _____ and _______ of the muscle insertion to determine the strongest point
length and angle
114
definition: condition when a body is completely motionless
static equilibrium
115
what is an example of static equilibrium
isometric muscle contraction
116
the net vector sum of static equilibrium is
zero
117
definition: point about which the body mass or weight is equally distributed and through which the force of gravity acts
center of gravity (CofG)
118
which method is based on the idea that every segment in the body has its own CoG?
segmental method
119
locating the center of gravity is important because mechanically, a body behaves as if all of its mass is _______ at the center of gravity
concentrated
120
when analyzing the human body's weight as a force for mechanical analyses, the vector representing that force is drawn through the body's _____ \_\_ \_\_\_\_\_\_
center of gravity
121
understanding the center of gravity is important for what two things?
1. stability
2. balance
122
definition: resistance to linear and or angular acceleration
stability
123
definition: ability to control equilibrium
balance
124
5 ways to increase stability (KEEP GOING YOURE STUDYING GREAT)
1. increase body mass
2. increase friction
3. increase size of support
4. horizontally position the CoG near the edge of support base on the edge of oncoming force
5. vertically position CoG as low as possible
125
definition: resistance to angular acceleration
inertia
126
inertia depends on mass of ____ and distribution of ____ relative to axis of rotation
body; mass
127
the closer the mass concentration is to the axis of rotation, the easier it is to...
cause a change in acceleration
128
what equation do we use when solving for body segments
I = mk squared
129
definition: prvents the rotating body from leaving its circular path while rotation occurs around a fixed axis
centripetal force
130
the direction of a centripetal force is always towards the
center of rotation
131
definition: a force of equal magnitude and opposite in direction created as a reaction to the centripetal force (newtons 3rd law...)
centrifugal force
132
when gravity is the only acting external force, the angular omentum is \_\_\_\_\_\_
conserved
133
the total H (angular momentum) of the system remains ______ in absence of external torques
constant
134
while H (angular momentum) is constant, angular velocities may be ________ from one axis or segment to another
transferred
135
momentum can be transferred from _______ to \_\_\_\_\_\_\_
angular to linear
136
definition: angular force (torque) acting over some time duration
angular impulse
137
angular impulse causes predictable changes in ______ \_\_\_\_\_\_\_\_
angular momentum
138
Linear vs. Angular
Mass (m) = ?
moment of inertia (I)
139
Linear vs. Angular
Force (F) = ?
Torque (T)
140
Linear vs. Angular
Momentum (M) = ?
Angular momentum (H)
141
Linear vs. Angular
Impulse (I) = ?
angular impulse (Tt)
142
4 muscles perform knee extension
rectus femoris, vastus medialis, vastus lateralis, mastus intermedius
143
3 muscles involved in knee flexion
semitendinosis, semimembranosis, biceps femoris
144
3 muscles ankle dorsiflexion
tibialis anterior, extensor digitorum longus, extensor hallucis longus
145
3 muscles ankle plantarflexion
gastrocnemius, plantaris, soleus
146
3 muscles ankle inversion
tibialis posterior, flexor digitorum longus, flexor hallucis longus
147
2 muscles ankle eversion
peroneus longus, peroneus brevis
148
3 muscles hip flexion
rectus femoris, iliacus, psoas major
149
4 musces hip extension
gluteus maximus, semitendinosus, semimembranosis, biceps femoris
