Exam 3 & Final Flashcards
(150 cards)
1
Q
What is “Pure Rotation”?
A
A term used when there is no linear motion of the axis of rotation.
2
Q
What is “General Motion”?
A
When rotation and translation occur at the same time.
3
Q
When you are closer to the joint do you have more or less linear rotation?
A
You will have less linear rotation when you are closer to the joint. Points further from the axis travel more.
4
Q
Do points on an axis of rotation travel?
A
No, unless there is general motion occuring.
5
Q
What are the angle measurements for angular kinematics?
A
Degrees, radians (57.3°/rad = 180/π)
6
Q
Is angular position (𝚯) a scalar or vector quantity?
A
It is a vector orientation relative to positive x-axis. 𝚯
7
Q
What plane of axis does angular rotation occur?
A
If an object is moving in the x,y plane, the axis for the vector is z.
𝛳= 30°k
8
Q
What is “Angular Displacement”?
A
It is the final position minus the initial position.
Δ𝛳= 𝛳f-𝛳i
9
Q
What is “Angular Distance”?
A
It is the angular length of path traveled.
𝛳1 + 𝛳2
10
Q
What is “Angular Velocity”?
A
The time rate at which an object rotates or revolves about an axis. ⍹ = average angular velocity = ▵𝛳/▵t
11
Q
What is “Angular Acceleration”?
A
A change in angular velocity of an object per unit of time. ⍶ = average angular acceleration = ▵⍹/▵t
12
Q
Does a positive average angular velocity (⍹) guarantee a positive average angular acceleration (⍶)?
A
No, just like linear acceleration, things can be positive in the negative direction.
13
Q
Is angular speed a vector or scalar quantity?
A
It is a scalar quantification of how fast an object is rotating independent of direction.
14
Q
Is angular speed a positive, negative, or zero value?
A
Angular speed is always a positive value.
15
Q
What is “Instantaneous Angular Speed”?
A
It is the magnitude of the instantaneous angular velocity vector (⍹)
16
Q
What is “Average Speed”?
A
It is the magnitude of the average angular velocity vector (⍹), but it could also be the angular distance/time.
17
Q
What is “Angular Speed”?
A
It is a scalar quantification of how fast an object is rotating independent of direction.
18
Q
Can you determine 𝚯, ⍵, ⍺ curves from one another?
A
Yes, just like linear PVA, you can find the instantaneous in the slope of a line.
19
Q
What are “Segment Angles”?
A
They describe orientation of a body segment. They are typically measured from horizontal axis at distal end. They are positive in the CCW direction.
20
Q
How to solve for segment angles
A
Set up right triangles with known side lengths using the coordinate data. Solve for appropriate angles in triangles, and adjust if needed.
𝛳thigh = 𝛳+90°
𝛳thigh = tan^-1(▵x/▵y) + 90° = 105°
21
Q
T or F
Your forearm and hand rotate about the elbow as you flex the joint. Assuming pure rotation about the elbow, the COM of your forearm and the COM of your hand will go through the same angular change but they will go through different linear change in position.
A
True
22
Q
T or F
When referring to the rotation of an object as “pure” rotation we are conveying that there is no change in the radius (length) of the object relative to its axis of rotation.
A
False
23
Q
T or F
A radian is a unitless quantity, coming from the ratio of the arc length of a circle divided by the radius of the circle
A
True
24
Q
T or F
Pi radians = 360 degrees
A
False
25
T or F
While PVA are vector quantities, the angular variables 𝚯, ⍵, ⍺ are scalar quantities
False
26
T or F
Similar to reporting a positive polar orientation of a vector as CCW, 𝚯⍵⍺ are also positive CCW relative to our positive x-axis
True
27
T or F
An object is changing orientation in the x-y plane making the rotation about the z-axis
True
28
T or F
While linear distance traveled of an object is always 0 or positive, the angular distance traveled of an object can be 0, +, or -
False
29
T or F
An object has negative angular acceleration. This means it is either speed up while rotating in the negative direction or slowing down while rotating in the positive direction
True
30
T or F
For a given radius of an object traveling on a circular path, doubling the angular velocity will double the centripetal acceleration. However, doubling the angular acceleration will quadruple the tangential acceleration
False
31
T or F
Centripetal and centrifugal are interchangeable terms, both referring to the linear acceleration of an object towards the axis of rotation
False
32
T or F
When performing the up phase of the biceps curl, beginning and ending with a pause, we would expect the magnitude of the centripetal acceleration of the barbell rotating about the elbow joint to first increase then decrease, reaching a peak near the middle of the up phase when the forearm is horizontal.
True
33
T or F
The instantaneous linear velocity of a point on a rotating object will always be tangent to the path. However, the resultant linear acceleration is not always perpendicular to the path
True
34
T or F
The body segment from the elbow joint to wrist joint is technically the "arm" segment. However, for clarity, we typically refer to it as the "forearm".
False
35
T or F
Segment angles are measured relative to the proximal end of a segment for the upper and lower extremities
False
36
Your segment angle vs time profile is a hill. We would expect the segment angular velocity vs time profile to be a ________
Hill-Valley
37
Joint angles can be calculated from _______
Known segment angles proximal and distal to the joint, and joint coordinate data and the Law of Cosines.
38
T or F
The included elbow joint angle will increase as you flex the joint and the excluded elbow joint angle will decrease as you flex the joint
False
39
In the Mimi et al (2004) article segment/joint angle definitions discussed in lecture, which were consistent with how we would want to define and name them
Knee angle
40
T or F
You roll two balls (without slipping). One has twice the radius as the other. For the same linear velocity of their COM, the ball with the smaller radius will have twice the angular velocity. However, the relationship between the radius of the ball and the angular velocity of the rolling ball is non-linear
True
41
What are the SI units for Torque (T)?
The SI units for Torque (T) are Nm. 1Nm = .7376ftlb
42
What does "Torque" do?
Torque (T) is the effect of a force that tends to cause a change in a body's state of angular position or motion.
43
What else is Torque referred as?
It is also known as "moment" or "moment of force". In biomechanics "moment" is typical and "M" is the variable.
44
What is the variable for "Moment"?
The variable for "moment" is "M"
45
What is "Torque"?
It is equal to the product of the magnitude of force (F) and its moment arm (r) with respect to the axis of rotation.
46
Is "Torque" a scalar or vector quantity?
Torque is technically a vector about the axis perpendicular to the plane of the force and moment arm.
47
What direction will indicate positive and negative torque.
CCW torque is positive. CW torque is negative.
48
What is a "Moment Arm"?
A moment arm (r) is perpendicular distance between the line of action of the force and the axis of rotation of the object.
49
How do you calculate torque?
Treat F and r as positive values, then assign +/- based on sense of turning.
50
Why do we want to avoid the term "Lever Arm"?
Some define it synonymous with moment arm, others define it as the distance from the axis of rotation to the point of application of the force. It's too unclear to use them interchangeably.
51
Can torque be a vector cross product?
Yes, one vector is the force and the other is a displacement vector. The displacement goes from the axis of rotation to point of application of the force. It is a very complicated way to calculate.
52
Resultant vs Resolved Force for Torque
Torque calculated from the resultant force will equal the sum of the torques produced by the individual components of the resultant force.
53
1 ftlb of torque is _____ 1Nm of torque
Greater than (1Nm = .7376 ftlb)
54
T or F
Torque is often referred to as a "moment" or "moment of force" in biomechanics with an "M" used as the variable instead of a "T". However, we will be sticking to referring to it as Torque and the variable "T" to avoid confusion.
True
55
T or F
Torque is a scalar quanitity that may either be positive or negative base on the direction of rotation that it will produce.
False. Torque is a vector.
56
T or F
When calculating torque you want to multiply the magnitude of the force with the length of the moment arm (both positive) and then assign it positive if it tends to rotate an object CW and negative if it rotates CCW when using our standard Cartesian coordinate system.
False
57
T or F
While some refer to the moment arm as the lever arm, not everyone defines the lever arm this way. Some define the lever arm as the straight line distance from the axis of rotation to the point of application of the force on the object. As such, it is best to avoid using the term lever arm.
True
58
T or F
The moment arm is the perpendicular distance (length) between the line of action of the force and the axis or rotation. As such, a vertical force will have a horizontal moment arm and a horizontal force will have a vertical moment arm.
True
59
You're working with the vertical force applied to your hand (FHy). The moment arm for this force relative to the axis of rotation should be labeled_____
rHy (r subscript Hy)
60
T or F
While not an intuitive way to calculate torque, it can be calculated as Fdsin𝛳. If the proper vector d and angle 𝛳 are selected, dsin𝛳 will equal the length of the moment arm.
True
61
T or F
If the resultant force creates a positive torque, then each of the resolved x and y force components are guaranteed to also produce positive torques.
False
62
T or F
As you perfrom the up phase of the biceps curl, the moment arm of the vertical force at the hand will be a maximum when the forearm and hand are horizontal mid phase and be much smaller at both the beginning and end of the phase.
True
63
T or F
As you perform the up phase of the biceps curl, the moment arm of the horizontal force at the hand will be a maximum when the forearm and hand are horizontal mid phase and be much smaller at both the beggining and end of the phase.
False
64
When examining the torque produced by the weight of the barbell about the elbow, such as what would exist when our biceps curl is performed quasi-statically, the magnitude of the torque will be _______ as the up phase is performed.
Increase then decrease
65
T or F
The moment of intertia is based on both the mass of the object and the distribiution of the mass relative to the axis of rotation with both having equal contribution to the value.
False
66
T or F
When referring to a rotating object as "rigid" we are conveying that there is no change in the radius (length) of the object relative to its axis of rotation. It will also have a constant mass moment of inertia about its axis of rotation.
True
67
T or F
Many of our body segments within the upper and lower extremeties have more mass towards their proximal ends compared to their distal ends. As such, this makes them easier to accelerate about their proximal joints than their distal joints.
True
68
T or F
Under angular conditions that satisfy Newton's 1st Law the sum of the external torques are zero. As such, the object must have a constant angular velocity, even if the moment of intertia about the axis of rotation changes.
False
69
T or F
In order to use the dynamic angular EOM (∑T = I⍺) the moment of intertia of the object about the axis of rotation must be constant.
True
70
T or F
WHen using the dynamic angular EOM (∑T = I⍺), you can always set up the equation about the object's COM, even if the actual rotation is occuring between a different axis.
True
71
T or F
While Newton's 1st and 2nd Law apply in both linear and angular motion, Newton's 3rd Law only applies to linear motion.
False
72
T or F
When setting up the angular EOM, every external force on the FBD will produce and external torque unless its line of action goes through the axis of rotaion used to set up the equation.
True
73
T or F
We can simplify our analysis of the FAH to assess the torque needed by muscles at the elbow to perform the biceps curly by including the barbell as part of the FBD. When this is done the forces of interaction between the hand and barbell become internal and are no longer on the FBD.
True
74
T or F
If we include all the potential external forces that act across the elbow joint when the forearm and hand is separated we will end up with both linear and angular EOM that are very complex and hard to solve. One way to get back to a more simplistic FBD that still allows for the complexity to exist is to "generalize" it at the elbow joint.
True
75
What is "Moment of Inertia"?
Moment of inertia or mass moment of inertia is a quantification of an object's resistance to changes in rotary motion. More mass = more rotation.
76
What are the units for moment of inertia?
The units are kg*m^2
77
Is moment of inertia a scalar or vector quantity?
Mass moment of inertia is a scalar quantity based on distribution of mass about the axis of rotation. It is always positive.
78
Does the distance of the mass from the axis of rotation impact inertia?
Yes, think of a baseball bat. It is much harder to get it to rotate when you are holding it by the handle trying to spin it.
79
How are body segment masses distributed?
Our upper arms, forearms, thighs, and lower legs have more mass towards their proximal ends.
80
What are the two benefits to body mass segment distribution?
It is easier to rotate by having mass near the proximal end.
Having a COM closer to the joint reduces the moment arm.
81
Angular Impulse-Momentum Relationship
An averaged form of Newton's 2nd Law. It is a net (sum) of external torques. It works with both constant and changing moment of inertia.
82
Angular Work and Power
Scalar (dot) product of two vectors about the z-axis. May be + or -. Must have angular kinematics in radians. Make sure linear and angular work/power are independent sources.
83
T or F
Your work is calculated to be positive, this also means that your average power will also be positive. It also means that at all times your instantaneous power during this time interval will be positive.
False
84
T or F
You are provided a work vs time plot of a movement. Since work is not instantaneous the plot is actually the rate of doing work at each instant in time.
False
85
If you create a FBD that includes an external force that most likely changes from positive to negative (or negative to positive) throughout the movement it might be best to draw the arrow with _______ direction.
Positive
86
When "giving" while landing from a jump we are attempting to reduce the _____ required to bring the COM velocity to zero.
Average ground reaction force applied to the person.
87
In polar notation is magnitude positive or negative?
Magnitude is always positive in polar notation.
88
Work is the area under the _______ curve
Force vs displacement and power vs time.
89
Your average force is 20N at a Polar angle of 40° and your displacement is 5m at Polar angle 110°. The work associated with the horizontal direction will be:
Negative
90
Your displacement is provided in polar as ▵P = 100m @ -120°, ▵Px =
-100cos(60°)m
91
Your displacement is provided in polar as ▵P = 100m @ -120°, ▵Py =
-100cos(30°)m
92
At the halfway point of the down phase of our biceps curl with the FAH horizontal, we would expect the instantaneous horizontal force applied by the hand to the barbell to be
Negative
93
At the halfway point of the down phase of our biceps curl with the FAH horizontal, we would expect the instantaneous vertical force applied by the hand to the barbell to be:
Upward and equal to the weight of the barbell.
94
What is a Single joint system?
A single joint system is looking at one joint, one segment, and one muscle.
95
What is a simple joint system?
A simple joint system is distilling a muscle and joint down to its basics in order to gain an understanding of how muscle force can cause/prevent motion or stabilize/destabilize a joint.
96
Tor F
Depending on your perspective, the acronym SJS could be Simple or Single joint system.
True
97
Tor F
Depending on your perspective, the acronym MTC could be Muscle-Tendon or Muscle-Tissue complex?
False
98
A muscle acting eccentrically is a:
Brake. It is associated with negative work.
99
T or F
A "typical" SJS FBD is described as being a single rigid segment with pure rotation about the joint of interest. Saying it is a single segment is a bit misleading, since it could actually be multiple segments merged into a single segment, such as the forearm and hand.
True
100
T or F
A "typical" SJS si analyzed under dynamic conditions (angular acceleration not equal to zero)
False
101
The weight force of our body segment is vertical, this makes the moment arm of the weight force relative to the joint the _______ distance.
Horizontal distance.
102
T or F
The "typical" SJS FBD can also be viewed as a lever system where a torque balance exists between the effort and resistance forces.
True
103
Our forearm and hand SJS FBD is a ____ class lever.
It is a third class lever
104
Most lever systems made from SJS are _____ class levers.
Most are third class levers.
105
T or F
The triceps surae is made up of three muscles that insert through the achilles tendon, the gastroc, soleus, and plantaris.
False, most people don't have the Plantaris muscle.
106
T or F
Anatomical pulleys typically increase the moment arm that the muscle has relative to the joint crossed.
True
107
T or F
While sesamoid bones are specifically designed to act as anatomical pulleys, other bones and even soft tissue can act as anatomical pulleys.
True.
108
T or F
Both the long head and short head of the biceps brachii have anatomical pulleys at both their origins and insertions
False
109
As we flex the elbow we would expect the angle of attachment of the biceps brachii (LH) to:
Increase
110
As we flex our elbow joint we would expect the moment arm of the biceps brachii (LH) relative to the elbow joint to:
Increase then decrease
111
T or F
Both linear and angular forms of energy are scalars and can be added to get the total energy (as long as they are from independent sources)
True
112
T or F
Just as we had two forms of PE when examining linear kinematics and kinetics, there are two forms of PE when examining angular kinematics and kinetics
False
113
The angular KE will ______ as the angular velocity increases (assuming all other components are held constant)
Increase non-linearly
114
T or F
When calculating angular KE the moment of inertia about the object's COM is always used, even when there is pure rotation about an axis not at the COM
False
115
The angular strain PE will _______ as the angular deformation increases (assuming all other components are held constant)
Increase non-linearly
116
If the up phase of our biceps curl is dynamic (but not ballistic) we would expect the muscle force to increase during the ______ up phase compared to the quasi-static version
First half
117
T or F
For typical muscles the whole muscle moment arm will be greatest near the mid-range of joint motion and decrease as the joint is moved closer to its extremes
True
118
Atypical whole-muscle moment arm profiles are most likely to occur at which joints:
Ankle and wrists
119
T or F
When resolving a muscle force into rotary and non-rotary components, the rotary component is tangent to the mechanical axis and the non-rotary component is perpendicular to the mechanical axis
False
120
T or F
While we may call it a non-rotary component of the muscle force, it actually has a non-zero moment arm relative to the joint and must be considered when calculating the torque produced by the muscle
False
121
As your angle of attachment goes from 0 to 90 degrees you would expect the non-rotary component to:
Decrease
122
As your angle of attachment goes from 0 to 90 degrees you would expect the rotary component to:
Increase
123
The moment arm for the rotary component of muscle force is the distance from the joint crossed to the muscle attachment along the mechanical axis. As long as there was no change in any anatomical pulleys at this attachment location as the angle of attachment goes from 0 to 90 degrees we would expect this moment arm to:
Stay the same
124
T or F
Conclusions drawn about the rotary and non-rotary components of a muscle force in one joint position tend to hold true throughout the whole range of motion for the joint.
False
125
For a given amount of torque needed form our muscle, as the attachment distance from the joint increases we would expect the muscle force needed to:
Decrease
126
T or F
While the non-rotary muscle force could be stabilizing or destabilizing, the rotary component of the muscle force is always stabilizing
False
127
T or F
While skeletal muscle and cardiac muscle have their contractile network on the inside of the cell and smooth muscle has it on the outside of the cell, they all use sarcomeres to generate force
False
128
T or F
Untrained muscle has a mechanical efficiency in the range of 20-25% with the rest given off as heat. With training we would expect to nearly double mechanical efficiency
False
129
_______ is the layer of CT that surrounds a fascile and _______ surrounds an individual muscle fiber
Perimysium, endomysium
130
T or F
Actin is also known as the "thin" filament in a sarcomere
True
131
When a sarcomere changes length the ______ band will change length
I Band
132
A muscle made up of three sarcomeres in series will be able to produce _____ the force of a muscle made up of three sarcomeres in parallel
1/3
133
T or F
Strap, Fusiform, and Triangular shaped muscles are all said to have their muscle fibers parallel to the LOA
True
134
T or F
Since pennate muscles have fibers offset from the LOA of the muscle, comparing two muscles with the same volume we would expect the strap muscle to produce more force along the LOA than the pennate muscle.
False
135
T or F
The main advantage of pennate muscles over strap muscles is their ability to shorten over greater distances due to longer fibers in the center of the muscle.
False
136
T or F
There has been some recent speculation that pennation angle may not have any functional significance. If this is true, when estimating maximum force capacity along the LOA of a muscle we should use the largest cross-sectional area perpendicular to the LOA not the PCSA
True
137
T or F
There is strong evidence that when comparing FT and ST fibers with the same PCSA that FT fibers can produce more force than ST fibers. Therefore, using 30 N/cm^2 to convert from PCSA to force should only be use with predominantly ST muscles.
False
138
T or F
The F0 predicted from PCSA and pennation angle is the maximum force that a muscle can transmit through the tendon onto the bone at its attachment and can not be exceed by any of the force modifiers.
False
139
T or F
When the force-length curve of many sarcomeres in both series and parallel combine into a whole muscle force-length curve, the max isometric active force typically occurs at 110% of resting length.
False
140
T or F
While you might find slightly different ranges of active force production quoted for a muscle, a typical range if from 60-160% of resting length.
False
141
T or F
In biomechanics we typically think about muscle activation level as going from 0-1 (0-100%), combining the number of motor units active and the twitch summation occurring within the motor units.
True
142
T or F
The activation level of a muscle does not alter the passive contribution of force from the internal connective tissue.
True
143
T or F
While sarcomeres in series are needed to increase the length over which a muscle can produce force, it comes at a cost. The sarcomeres in series are not able to do as much work as those that are arranged in parallel.
False
144
Most uni-articular muscles operate on the ascending limb and plateau of their force-length curve. The ascending limb is when the muscle is ______ resting length.
Shorter than
145
T or F
We would expect standing calf raises with the knee extended to work the soleus harder and seated calf raises with the knee flexed to work the gastroc harder.
False
146
T or F
While definitive evidence is lacking, chronic training in limited ranges of joint angles can probably adjust the resting length of muscles through addition/subtraction of sarcomeres in series within the muscle.
True
147
T or F
The force-velocity curve of muscle within the concentric region is actually a straight line when fresh and only starts to "sag" when fatigue sets in.
False
148
T or F
When examining maximum shortening velocity we would expect a muscle with 60% FT fibers to have a greater maximum shortening velocity than a muscle with 40% FT fibers.
False
149
When max active muscle force is reduced while the other characteristics of muscle is kept constant what changes would we expect in the instantaneous power profile:
Reduced peak power output
150
