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Biomechanics > Exam 2 Review Questions > Flashcards

Exam 2 Review Questions Flashcards

1
Q

When a pendulum starts from rest and swings 20 degrees in 2 seconds, the average angular velocity is:

A

10 Degrees

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2
Q

True or False? When swinging your extended arm around in a circle (in a sagittal plane), your elbow has a greater arclength than your wrist?

A

False

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3
Q

If a pendulum swings forward 30 degrees and then back 10 degrees, the angular distance and displacement are:

A

distance: 40 degrees, displacement: 20 degrees

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4
Q

True or false? If a body is rotating with a constant angular velocity, the angular acceleration AND the linear, centripetal acceleration of the body are zero.

A

False,

Even with no angular acceleration, constant angular motion gives rise to a nonzero centripetal acceleration.

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5
Q

The lowercase, Greek letter omega is the symbol used for angular acceleration.

A

False

Alpha

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6
Q

True or False? If a body segment is rotating with a constant angular velocity, the angular acceleration of the segment AND the linear, tangential acceleration of a point on the distal end of the segment are zero.

A

True

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7
Q

True or False? One degree is larger than one radian?

A

False

a radian is larger than a degree

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8
Q

The linear velocity of a point on a body undergoing angular motion is equal to?

A

(radius)*(angular velocity) where radius is the distance from the axis of rotation to the point.

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9
Q

An angle calculated between the thigh and a horizontal plane is?

A

An absolute angle

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10
Q

Angular velocity is measured in what units?

A

Radians/seconds

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11
Q

What is the angle of the knee joint in the anatomical position?

A

180degrees

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12
Q

With a constant, non-zero angular velocity, the tangential linear velocity of a rotating point about the axis is:

A
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13
Q

For a given angular velocity of a golf swing, the linear velocity of the head (distal end) of a long club compared to a short club will be:

A
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14
Q

The motion of the arm during a properly executed throwing motion is such that:

A

the proximal segments begin to rotate prior to the distal segments.

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15
Q

Consider a person standing in the anatomical position. The moment of inertia of the body rotating about the longitudinal axis is __________ the moment of inertia about the anteroposterior axis.

A
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16
Q

What is the biomechanical purpose of the patella?

A

It increases the moment arm of the knee extensors, thus creating more torque for a given muscle force.

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17
Q

Angular momentum can be expressed mathematically as:

A

moment of inertia * angular velocity

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18
Q

True or False? Angular momentum of a body is not influenced by the application of linear forces to the body

A

False

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19
Q

As moment of inertia decreases what happens to angular velocity and angular momentum?

A
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20
Q

he moment of inertia of a moving body is specific to the:

A

Axis of Rotation

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21
Q

During a dive, if a diver goes from a full layout position to a tuck position, what will happen to her angular velocity?

A

Increase

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22
Q

Torque is the angular analog of what?

A

Force

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23
Q

Units for angular momentum and torque?

A

Angular Momentum: kg m^2/sec
Torque: Newton (N)

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24
Q

Joint torque is influenced by:

A
  1. Muscle Force
  2. Moment Arm
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25
Q

True or False? The torque experienced by a system is the angular effect of the linear forces applied to it

A

True

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26
Q

Moment of inertia is the angular analog of what?

A
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27
Q

If angular momentum is NOT conserved, what measure will allow us to predict changes in angular momentum?

A
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28
Q

When the knee is flexed from anatomical position, what happens to the moment of inertia about the vertical axis of the hip?

A

increased

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29
Q

When knee is flexed from anatomical position, what happens to the moment of inertia of the leg about the medio-lateral axis at the hip?

A

decreased

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30
Q

In a movement where angular momentum is conserved there must be:

A

No net external torque

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31
Q

A tailwind acting to push a sprinter during a 100 m race would increase the relative velocity of the runner in regard to the air, decreasing the race time for the sprinter.

A
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32
Q

What is Center of Pressure

A

The point of application of a dynamic fluid force acting upon a body

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33
Q

True or False?

A tailwind acting to push a sprinter during a 100 m race would increase the relative velocity of the runner in regard to the air, decreasing the race time for the sprinter.

A

False

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34
Q

True or False?

Consider two objects with the same size, shape, and velocity but different masses flying through the same air at the same time, although the same drag force is applied to both objects the EFFECT of the force on the momentum of each is different.

A

True

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35
Q

SI unit for Density

A

Kg/m^3 (kilogram per cubic meter)

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36
Q

What orientation do drag and lift act in relation to one another?

A

Always perpendicular (90 degrees)

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37
Q

Where does the buoyancy force act upon a body?

A
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38
Q

Laminar flow

A

A flow characterized by smooth, parallel layers

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39
Q

Factors that influence drag

A

-fluid density
-projected area
-coefficient of drag
-Relative velocity

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40
Q

What is viscosity?

A

The resistance to float

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41
Q

What are the components of dynamic fluid force?

A

Drag and Lift

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42
Q

What is the SI unit of specific weight?

A

N/m^3 ( Newtons per cubic meters)

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43
Q

True or False?

The bouyant force exerted on an object is due to the relative motion of that object in the fluid

A

False

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44
Q

Fluid Related Forces

A

Drag
Lift
Buoyancy
Overall Fluid Resistance

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45
Q

True or False?

One cubic meter of air is heavier than one cubic meter of water

A

False

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46
Q

True or False?

The buoyancy of a swimmer is influenced by the total body volume of a swimmer

A

False: only the submerged volume.

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47
Q

What is Magnus Force

A

lift force created by spin

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48
Q

What is the Magnus Effect?

A

deviation in trajectory of a spinning object toward the direction of spin

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49
Q

The dimples of a golf ball allow it to fly further in the air by decreasing the:

A

Form Drag

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50
Q

For a ball moving through the air, which of the following pairs of velocities represent the highest relative velocity?

A

ball v = -20 m/s; air v = 20 m/s

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51
Q

The point of application of a bouyancy force acting on an object is at the ________________ of the object.

A

Center of Volume

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52
Q

The point of application of a dynamic fluid force acting upon a body is at the ____________ of the body.

A

Center of Pressure

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53
Q

What type of angle is shown?

A

relative angle

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54
Q

What type of angle is shown?

A

Absolute angle

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55
Q

r

A

radius

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56
Q

α

A

angular acceleration

57
Q

ω

A

angular velocity

58
Q

a (subscript r)

A

radial acceleration

59
Q

Σ

A

the sum of

60
Q

Which of the following factors influence muscle force production?

Myofilament type
Physiological cross sectional area
Muscle gender
Muscle location

A

PCSA

61
Q

Torque depends on which of the following?

Magnitude of Force
Point of force application
moment arm of the force
all of the above

A

All of the above

62
Q

Which of the following depicts moment arm?

A

C

63
Q

When the forearm is in a state of static equilibrium (i.e., no movement):

All torques must sum to zero
All torques must sum to a positive number
All torques must sum to a negative number
I have no clue what you are asking

A

All torques must sum to zero

64
Q

The center of gravity of the body is:

a fixed, never-to-move, point in the body
a point around which body weight is equally distributed
a point which is NOT influenced by the motion of arms and legs

A

A point about which body weight is evenly distributed

65
Q

Consider the elbow flexor, biceps brachii. What elbow joint angle results in the largest moment arm for this muscle?

30 degrees
60 degrees
90 degrees
135 degrees

A

90 degrees

66
Q

If there are three eccentric forces and two centric forces acting about the elbow how many torques are acting about the elbow?

A

3

67
Q

What is a radian?

A

the ratio between the circumference of a unit circle and the length of its radius (1)

68
Q

Relative Angle

A

Joint angle, angle of two segments

69
Q

Absolute angle

A

Angle between a segment and a reference plain (i.e. shank wrt horizontal plane)

70
Q

Joint angle is represented by which greek letter?

A

theta

71
Q

Hypersupination

A

arch strike excessive load on fibula

72
Q

Hyperpronation

A

Collapsing arch (instep strike) excessive load on tibia

73
Q

Unit for angular displacement

A

radians

74
Q

degrees to radians

A

(deg) * pi / 180

75
Q

tangential velocity units

A

radians/s

76
Q

how does radius effect velocity?

A

longer radius greater velocity

77
Q

Correct anatomical throwing sequence

A

proximo distal
pelvis trunk upper arm forearm hand

78
Q

Angular Acceleration Units

A

rad/s squared

79
Q

Tangential Aceleration definition

A

linear acceleration of a point of interest

80
Q

Centripital Acceleration Synonym

A

Radial acceleration

81
Q

Radial Acceleration definition

A

rate of chagne in direction of a body in angular motion

82
Q

For a given r, higher Vt is related to higher what?

A

radial acceleration

83
Q

What do rotational and curvilinear motions result in?

A

radial acceleration

84
Q

Centrifugal Forces

A

force that acts outward on a body moving around a center, arising from the body’s inertia.

85
Q

Centripital Force

A

a force that acts on a body moving in a circular path and is directed toward the center around which the body is moving.

86
Q

Consider a yoyo being spun in the air which component demonstrates centripital force?

A

the string pulling the yoyo in

87
Q

Considera yoyo being spun in the air which component demonstrates centrifugal force

A

the yoyo at the end, if released would fly outward

88
Q

Linear and Angular analogs
d
v
a

A

theta
little omega
little alpha

89
Q

If the angular acceleration of the forearm is zero, then:

1 angular velocity is zero
2 angular velocity is constant
3 both 1 & 2 could be correct
4 neither 1 nor 2 are correct

A

3

90
Q

True or false: Joint angles are relative angles

A

True

91
Q

Rearfoot angle is calculated from two segment angles, which are measured in the ______ plane.

A

Frontal Plane

92
Q

RF angle

A

Rearfoot Angle

93
Q

Units of tangential acceleration

A

m/s squred

94
Q

When running around a curve on the track, in which lane is it more difficult to maintain your direction, with the same linear velocity (i.e., you have a higher centripetal acceleration)?

1 Outside
2 Inside
3 Centripetal acceleration is same for all lanes

A

Inside

95
Q

What are the units of centripetal acceleration?

A

m/s squared

96
Q

If there are three eccentric forces and two centric forces acting about the elbow how many torques are acting about the elbow?

A

3

97
Q

Moment of intertia depends on which elements?

A

Mass and Distribution of mass

98
Q

What are the units of radial acceleration?

A

m/s squared

99
Q

What does resistance to angular motion depend on?

A

Distribution of mass
Mass

100
Q

Radius of gyration symbol

A

k

101
Q

What is radius of gyration

A

represents the object’s mass distribution with respect to a give axis of rotation.

102
Q

Newtons 1st law of angular momentum

A

a rotating body will maintain a state of constant angular motion unless acted on by an external torque

103
Q

Newtons second law

A

T= I alpha
a net external torque exerted on a body is directly proportional to the rate of change in angular momentum (angular motion)

104
Q

Newtons third law of angular motion

A

for every torque exerted on one body there is an equal and opposite torque exerted by a second body on the first

105
Q

The moment arm associated with a torque is:

A

a distance which is perpendicular to the force

106
Q

If you hold a cat upside down and drop it, the cat’s TOTAL angular momentum during flight will be:

A

Zero the entire flight

107
Q

If the angular acceleration of the forearm is zero, then:

A

angular velocity is zero
angular velocity is constant

108
Q

Fluid Definition

A

A substance that flows when subjected to a sliding force

109
Q

Four Properties of a Fluid

A

Pressure
Density
Specific Weight
Viscosity

110
Q

Pressure

A

Force / area n/m squared

111
Q

Density

A

littel rho
mass / volume kg/m cubed

112
Q

specific weight

A

little gamma
weight / volume n/m cubed

113
Q

Viscosity

A

resistance to flow (internal friction)

114
Q

Two types of flow

A

laminar
turbulent

115
Q

laminar flow

A

fluid molecules lowing parallel to one another, smooth, ordered

116
Q

turbulent flow

A

fluid molecules mix in a random manner, chaotic, onordered

117
Q

Fluid forces

A

Immersion : buoyancy
Dynamic: Drag and Lift

118
Q

Drag and Lift make up?

A

total fluid resistance

119
Q

buoyancy

A

upward force
fluid reaction force

120
Q

archimedes principle

A

buoyant force is equal to the weight of the fluid displaced by the body (Fb= Vd(gamma)

121
Q

Formula for determining if an object will float?

A

Fb= BW

122
Q

Density of air

A

1.2 kg/m cubed

123
Q

buoyancy of air

A

1N (.2lbs)

124
Q

when will a body experience a buoyant force?

A

When it is immersed in fluid

125
Q

When will a dynamic fluid force occur?

A

when relative motion occurs between the body and the fluid

126
Q

Drag

A

opposes motion

127
Q

lift

A

acts perpendicular to flow

128
Q

relative velocity

A

vfluid - vbody

129
Q

types of drag

A

surface drag
form drag

130
Q

surface drag

A

force acting on the surface of a body (skin friction)

131
Q

How is surface drag reduced?

A

reducing roughness or surface area

132
Q

form drag

A

force created by pressure difference between front and back sides of a body

133
Q

how is form drag reduced?

A

streamlining, dimples on golf ball

134
Q

terminal velocity

A

acceleration equals zero

135
Q

lift

A

force acting perpendicular to fluid flow

136
Q

magnus effect

A

deviation in trajectory of a spinning object toward the direction of spin lift force created by spin

137
Q

Overall Air Resistance

A

Resultant vector of lift and drag
OAR squared = lift squared + drag squared

138
Q

What is the buoyancy force a reaction to?

A

weight of the fluid displaced

Biomechanics (11 decks)

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