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Biomechanics > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

definition: forces that cause motion or are caused by motion

A

linear kinetics

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2
Q

example of linear kinetics

A

gravity, impact force,

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3
Q

Newtons laws: the basis of ______

A

mechanics

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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

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5
Q

definition: the quantity of motion a body possesses (body must be moving)

A

momentum

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6
Q

what is the equation for momentum?

A

M = m x v

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7
Q

how does momentum change?

A

by changing mass or velocity

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8
Q

in absence of _____ ______, the total momentum of a given system remains constant

A

external forces

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9
Q

definition: objects in a head on collision bounce off each other. combined momentum is conserved

A

elastic collision

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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

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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

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12
Q

what is the equation for newtons 2nd law of motion

A

F = m x a force = mass x acceleration

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13
Q

impulse is the product of _____ times ____

A

force times time

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14
Q

if an impulse acts on a system, it will change the ______ _____ of the system.

A

total momentum

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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

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16
Q

in impulse equations, what must mass be in ?

A

Kg

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17
Q

what is newtons third law?

A

law of action-reaction: for every action there is an equal and opposite reaction

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18
Q

what is an example of newtons 3rd law?

A

ground reaction force

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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

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20
Q

What is a common force we can use to our advantage?

A

Ground reaction force

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21
Q

Jumpers use ground reaction force to convert ______ velocity to ______ velocity

A

horizontal to vertical

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22
Q

runners can experience _____ due to GRF

A

injuries

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23
Q

GRF & ______ data can determine the amount of _____ at each joint

A

kinematic; force

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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

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25
Q

force pattern varies with running _____

A

style

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26
Q

GRF can be measured by a

A

force palate (precise scale that measures forces in 3 dimensions – x,y,z)

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27
Q

4 factors influencing GRF

A
  1. running speed 2. footwear 3. ground surface 4. grade of surface
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28
Q

(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.

A

gravitation; proportional; inversely

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29
Q

definition: collision of two bodies in a small amount of time

A

impact

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30
Q

3 types of impact

A
  1. perfectly elastic 2. perfectly plastic 3. somewhere in between
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31
Q

what type of impact: the velocities of the 2 bodies remain equal before and after impact. example?

A

perfectly elastic. ball bouncing

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32
Q

what type of impact: at least one body deforms and does not regain its original shape and bodies do not separate. Example?

A

perfectly plastic. car crash

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33
Q

definition: a unit-less number between 0 and 1 that is used to describe the relative elasticity of an impact

A

coefficient of restitution

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34
Q

what does the number 1 represent ? the number 0 ?

A

1 = perfectly elastic 0 = perfectly plastic

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35
Q

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.

A

collision; proportional

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36
Q

what does Hb stand for? Hd?

A

Hb = bounce height Hd = drop height

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37
Q

What unit does the coefficient of restitution use?

A

none. it’s a unit less number

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38
Q

work is the produce of _____ and _______ (distance)

A

force and displacement

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39
Q

what is the equation for work?

A

U = fd

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40
Q

definition: the object is moved in the same direction of the force

A

positive work

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41
Q

definition: the object is moved in the opposite direction of the force

A

negative work

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42
Q

what type of work do eccentric and concentric muscle contractions do?

A

concentric = positive work eccentric = negative

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43
Q

definition: rate of mechanical work

A

power

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44
Q

what unit is used to represent power?

A

watt

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45
Q

capacity of a body to do work

A

mechanical energy

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46
Q

3 types of mechanical energy

A
  1. kinetic 2. potential 3. strain
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47
Q

energy in motion

A

kinetic energy

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48
Q

energy due to position

A

potential energy

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49
Q

KE = ?

A

1/2 mv squared

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50
Q

PE = ?

A

weight x height OR mass x height x gravity

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51
Q

energy of elasticity stored energy in the deformation of an object

A

strain energy

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52
Q

example of strain energy?

A

pole vault pole, tendons

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53
Q

Strain energy (SE) = ?

A

1/2 kx squared k = stiffness, x = length

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54
Q

when gravity is the only acting external force, a body’s mechanical energy remains ______

A

constant (law of conservation of energy)

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55
Q

the work of a force is equal to the change in energy that it produces in the object acted on it

A

principle of work and energy

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56
Q

what is the equation for conservation of energy?

A

1/2mv squared = mgh (KE equation = PE equation)

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57
Q

torque is a moment of _____

A

force

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58
Q

torque is a _____ effect created by an applied force

A

rotary

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59
Q

torque is the ______ equivalent of linear force

A

angular

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60
Q

what is the equation for torque with a 90 degree angle?

A

T = F x r

61
Q

a force applied through a body’s ______ of rotation results in linear motion or no motion depending on the _____ of force applied

A

center; amount

62
Q

greater torque results in a greater tendency for _____ to occur and a greater angular _______

A

rotation; acceleration

63
Q

definition: perpendicular and shortest distance between a force’s line of action and axis of rotation

A

moment arm

64
Q

any deviation from the _______ will change the moment arm length

A

perpendicular

65
Q

definition: pair of equal and opposite forces that produce torque in the same direction

A

force couple

66
Q

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

A

magnitude, added

67
Q

counterclockwise rotation is ______; clockwise rotation is _______

A

positive; negative

68
Q

when examining the direction of joint rotation, what two things are important?

A
  1. position of the body 2. position of the person observing the movement (could be clockwise or counterclockwise depending on stance)
69
Q

Joint torques produce movement of _____ _____

A

body segments

70
Q

Muscles (through ____) pull on points across a center of rotation (_____), thus creating _______

A

tendons, joints, torques

71
Q

agonistic and antagonistic muscles are working so the change in joint position is a result of ____ _____

A

net torque (whichever is greater produces net torque)

72
Q

what 5 things are joint torques influenced by ?

A
  1. segment weight 2. segment motion 3. segment length 4. external motion 5. external forces (weight, pulley system, etc.)
73
Q

what is the equation for torque when the angle is other than 90 degrees?

A

Fc = rF x sin0

74
Q

_____ torques can be measured directly or indirectly

A

joint

75
Q

to measure joint torques directly, place a strain gauge in the ______

A

muscle

76
Q

how could you measure joint torques indirectly?

A

Electromyography (EMG) Isokinetic device

77
Q

what does indirect measuring, measure?

A

torque, segment motion (used in physical rehabilitation and for bilateral comparison)

78
Q

definition: a rigid bar rotating around about an axis or fulcrum

A

levers

79
Q

a bone is an example of a ____ and a joint is an example of a _____

A

bar; fulcrum

80
Q

the force applied by levers will move a ______

A

resistance

81
Q

three types of levers

A

first second third class levers

82
Q

example of first class lever, and one example in the body

A
  • see saw - triceps
83
Q

example of second class lever & one example in the body

A
  • wheelbarrow - calf-muscle
84
Q

example of third class lever & one in the body

A
  • broom - biceps
85
Q

which lever is the most common in the body?

A

third class levers

86
Q

WHAT CLASS lever is this

A
87
Q

what class lever is this?

A
88
Q

what class lever is this

A
89
Q

2 purposes of levers

A
  1. gain mechanical advantage
  2. gain a greater range of motion
90
Q

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?

A

Second class lever. (few muscles are set up this way, but calf muscles are; wheelbarrow)

91
Q

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?

A

3rd class levers; most joints in our bodies

92
Q

mechanical advantage = ?

A

moment arm force / moment arm resistance

93
Q

if the mechanical advantage value is:

> 1, < 1 or = 1

A

> 1 (gain mechanical advantage)

< 1 (lose mechanical advantage)

= 1 (no mechanical advantage)

94
Q

if the value is > 1, the force required is ____ than the resistance

A

less

95
Q

if the value is < 1 the force required is _____ than resistance

A

greater

96
Q

most levers in the human body are ____ class and their mechanical advantage is ___ 1.

A

3rd class; < 1

97
Q

in the human body lever rom and speed are ______

A

emphasized

98
Q

for joint movement to occur in the body muscle frces generated must be in _____ of ______ forces

A

in excess of resistance forces

99
Q

definition: the only force component that will cause the bone to rotate around the joint center.

A

rotary component

100
Q

the rotary component is ______ to the bone and is known as the __ component

A

perpendicular; y component

101
Q

definition: the component of the force parallel to the bone, pulling the bone away from the joint center

A

dislocating component

102
Q

definition: the component of force that is parallel to the bone, pulling the bone toward the joint center

A

stabilizing component

103
Q

both of the dislocating component and the stabilizing component can be part of the __ component

A

x

104
Q

whent a lever has an angle < 90 degrees, it has both a rotary (y) component and a ______ (x) component

A

dislocating (since its pulling it away from the joint center

105
Q

when the lever has an angle > 90 degrees, it has both a rotary (y) component and a ______ (x) component

A

stabilizing (bc its pulling toward joint center)

106
Q

when the lever has a 90 degree angle, is has a 100% ____ component

A

rotary component; 100% of the force of the tendon causes rotation

107
Q

as we move a joint through its range of motion, the muscle that is moving the joint is _____ and more _____ at different joint angles

A

stronger; stable

108
Q

the specific joint _____ in which the muscle is stronger/stable ____ from person to person and joint to joint

A

angles; varies

109
Q

angles are in reference to the _____ compared to the bone and not bone compared to bone

A

muscle

110
Q

the position of the muscle relative to the bone will change the joint ____

A

angle

111
Q

force generated (strength) during elbow flexion is highest at __ degrees (joint angle)

A

80

112
Q

the _______ of the muscle determines the force generated

A

length

113
Q

look at muscle _____ and _______ of the muscle insertion to determine the strongest point

A

length and angle

114
Q

definition: condition when a body is completely motionless

A

static equilibrium

115
Q

what is an example of static equilibrium

A

isometric muscle contraction

116
Q

the net vector sum of static equilibrium is

A

zero

117
Q

definition: point about which the body mass or weight is equally distributed and through which the force of gravity acts

A

center of gravity (CofG)

118
Q

which method is based on the idea that every segment in the body has its own CoG?

A

segmental method

119
Q

locating the center of gravity is important because mechanically, a body behaves as if all of its mass is _______ at the center of gravity

A

concentrated

120
Q

when analyzing the human body’s weight as a force for mechanical analyses, the vector representing that force is drawn through the body’s _____ __ ______

A

center of gravity

121
Q

understanding the center of gravity is important for what two things?

A
  1. stability
  2. balance
122
Q

definition: resistance to linear and or angular acceleration

A

stability

123
Q

definition: ability to control equilibrium

A

balance

124
Q

5 ways to increase stability (KEEP GOING YOURE STUDYING GREAT)

A
  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
Q

definition: resistance to angular acceleration

A

inertia

126
Q

inertia depends on mass of ____ and distribution of ____ relative to axis of rotation

A

body; mass

127
Q

the closer the mass concentration is to the axis of rotation, the easier it is to…

A

cause a change in acceleration

128
Q

what equation do we use when solving for body segments

A

I = mk squared

129
Q

definition: prvents the rotating body from leaving its circular path while rotation occurs around a fixed axis

A

centripetal force

130
Q

the direction of a centripetal force is always towards the

A

center of rotation

131
Q

definition: a force of equal magnitude and opposite in direction created as a reaction to the centripetal force (newtons 3rd law…)

A

centrifugal force

132
Q

when gravity is the only acting external force, the angular omentum is ______

A

conserved

133
Q

the total H (angular momentum) of the system remains ______ in absence of external torques

A

constant

134
Q

while H (angular momentum) is constant, angular velocities may be ________ from one axis or segment to another

A

transferred

135
Q

momentum can be transferred from _______ to _______

A

angular to linear

136
Q

definition: angular force (torque) acting over some time duration

A

angular impulse

137
Q

angular impulse causes predictable changes in ______ ________

A

angular momentum

138
Q

Linear vs. Angular

Mass (m) = ?

A

moment of inertia (I)

139
Q

Linear vs. Angular

Force (F) = ?

A

Torque (T)

140
Q

Linear vs. Angular

Momentum (M) = ?

A

Angular momentum (H)

141
Q

Linear vs. Angular

Impulse (I) = ?

A

angular impulse (Tt)

142
Q

4 muscles perform knee extension

A

rectus femoris, vastus medialis, vastus lateralis, mastus intermedius

143
Q

3 muscles involved in knee flexion

A

semitendinosis, semimembranosis, biceps femoris

144
Q

3 muscles ankle dorsiflexion

A

tibialis anterior, extensor digitorum longus, extensor hallucis longus

145
Q

3 muscles ankle plantarflexion

A

gastrocnemius, plantaris, soleus

146
Q

3 muscles ankle inversion

A

tibialis posterior, flexor digitorum longus, flexor hallucis longus

147
Q

2 muscles ankle eversion

A

peroneus longus, peroneus brevis

148
Q

3 muscles hip flexion

A

rectus femoris, iliacus, psoas major

149
Q

4 musces hip extension

A

gluteus maximus, semitendinosus, semimembranosis, biceps femoris

Biomechanics (10 decks)

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