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EPHE 201 - Qual Analysis > Final Joke > Flashcards

Final Joke Flashcards

1
Q

Angular Inertia

A

Property of an object to resist changes in angular motion

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2
Q

What affects Angular Inertia

A
  • the mass of an object

* the distribution of mass of an object relative to the axis of rotation.

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3
Q

Moment of Inertia

A
  • Quantification of Angular Intertia
    -Can be distributed among multiple axis of rotation
    • an object is composed of many particles of matter all with a certain mass. Each particle resists motion. The greater the distance that particles are located away from the axis of rotation the harder it is to rotate.
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4
Q

Moment of Inertia Equation

A

I = mk2
This equation states that moment of inertia (I) is dependent on the mass of the object (m) and the distance from the mass to the axis of rotation (k).

• This equation shows that distribution of mass (k) has a greater
influence on angular inertia than mass (m) does

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5
Q

The Radius of Gyration (K)

A

The length measurement that represents the concentrated mass of the object from the axis of rotation…well not quite…

Really just think of k as the term quantifying the distribution of mass

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6
Q

Angular Momentum

A

L = Iw
Angular momentum is defined as the tendency for an object to remain in angular motion.

• Angular momentum (L) is determined by the moment of inertia of an object and it’s angular velocity (w).

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7
Q

If the Moment of Inertia Changes, what happens to the Angular Velocity

A

If the moment of inertia changes, the angular velocity of the object will change to maintain the same momentum.

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8
Q

Newton’s Second Law as it pertains to angular kinetics

A

If a net external force is exerted on an object at a
distance from the axis of rotation, the object will
accelerate angularly in the direction of the net external
torque, and its angular acceleration will be proportional
to the net external torque and inversely proportional to
its moment of inertia.

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9
Q

Angular Impulse

A

Angular Impulse is a measure of a torque applied for a
certain amount of time

Angular Impulse = Torque X time
J = Mt

• The net torque acting over some interval of time will cause a change in angular momentum of an object.

ex) • A diver must maximize the time that the force can
be applied by having a large moment of inertia but
then quickly minimize the moment of inertia to
increase his angular velocity.

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10
Q

Work

A

• Work is the product of force and the displacement in the direction of that force.

U = Fd

  • U is the work done on an object
  • F is the force applied to the object
  • d is the displacement of the object in the line of action of the force.
  • The unit of measurement is a joule or ft.lb or N.m (=joule)
  • If you move an object a certain distance you have done work on that object
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11
Q

What Happens When a Weight Lifter lifts weights

A

• But what if the weightlifter lifts the weight and then lowers the weight.

• The displacement will be zero.
• The work will also be zero, even though the
weightlifter definitely expended energy.

• There was physiological work done
by the lifter however, there was no
overall mechanical work because the
weight is in the same position.

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12
Q

Positive and Negative Work

A

• Positive work is done when a force displaces an object in the same direction as the
force. = Concentric muscle contractions
• For example a pitcher does positive work against a baseball when throwing it.

  • Negative work is done when the object is displaced in the direction opposite the force = Eccentric Muscle Contractions
  • For example, the weightlifter lowering the weight
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13
Q

Energy and its two types

A
  • Energy is the capacity (or ability) to do work.
  • Heat, light, sound, chemical, mechanical.
  • Kinetic energy
  • Potential energy.
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14
Q

Kinetic Energy

A

Due to motion

• if one object, in motion, hits another object, the moving object does work on the second object and vice versa.

KE = ½ mv2

• The units are kg m2/s2 which is the same as N.m so the units are
the same as work.
• Determining kinetic energy is easier than determining work because we can measure mass and velocity a lot easier than measuring force.

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15
Q

Potential Energy

A

Due to position

  • Potential energy comes in two forms;
  • Gravitational potential energy
  • Which is energy due to the position of an object relative to the earth
  • Strain energy
  • Which is energy due to the deformation of an object.
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16
Q

Gravitational Potential Energy

A

• This energy is related to the weight of an object and its elevation or height above the ground or some reference.

  • PE = mgh Or PE = Wh (W for weight)
  • The units for gravitational potential energy are N.m (joules)
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17
Q

Strain Energy

A

Related to an objects stiffness, its material properties and its deformation
• strain energy in the deformed pole in pole vault.
• In the board in spring board.

  • The greater the deformation of the object the greater the strain energy.
  • There is energy being stored in the deformed object

SE = 1/2kx2

• k is the spring constant or stiffness constant of the material normally
measured in N/m
• x is the amount of deformation

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18
Q

Energy Conservation

A

• The law of conservation of energy states that the total amount of energy in a system remains constant (“is conserved”), although energy within the system can be changed from one form to another or transferred from one object to another.

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19
Q

Pole Vaulting with energy

A
  • As the pole vaulter runs toward the bar, he gains kinetic energy.
  • As he bends the pole, he does work on the pole and stores elastic potential energy in the pole.
  • The stored elastic potential energy is converted into gravitational potential energy as the pole does work on the pole vaulter to lift them high above the ground.
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20
Q

Work - Energy Relationship

A

Essentially if we exert work on an object horizontally the work will be converted into kinetic energy and accelerate the object until another external force acts on the object to produce a negative work

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21
Q

Power

A

• Power is the rate of doing work
P = U/t
or
P = Fv.

Power is described as the ability to exert a force over a distance in a certain amount of time. Power can be considered how fast or slow work is done.

• The units of power are watts or joules/s another unit of power is
horsepower.

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22
Q

Remember moving books with Power

A 
Do you
• Move all the books at once.
• High force, low velocity
Or
• Move the books one at a time
• Low force, high velocity
Or
• something in between.
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23
Q

Power in Muscles

A
  • As contraction velocity increases our ability to produce force decreases
  • As contraction velocity decreases our ability to produce force increases.
  • Think about trying to lift light and heavy weights at the gym
  • It is easy to lift a light weight quickly but not a heavy weight.
  • This best choice would be at a medium force and a medium velocity.
  • On average the maximum power output occurs at a velocity of approximately 35-60% of the muscles maximum contraction velocity.
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24
Q

Two Types of Fluid Forces

A

A buoyant force
• Due to immersion in fluid

A dynamic force
• Due to relative movement in fluid
• Lift force
• Drag force

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25
Q

Buoyant Force

A 
• An object submerged in water
will experience
• pressure from the weight of the
water above
• Pressure from the water beside
• Pressure from the water below to
hold up the object and the water
above the object

Rlower-Rupper = buoyant force

• As you submerge an object
deeper and deeper in water the
force (pressure) above and the force (pressure) below increase. The pressure below the submerged object will always be greater than the pressure above.

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26
Q

Archimedes Principle

A
  • The difference between the force above and force below will always be related to the weight of the volume of fluid displaced
  • So the buoyant force will always be acting up on the object and will be related to the weight of the fluid displaced
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27
Q

Results of the Buoyant Force

A

If buoyant force = mg, object will be in static equilibrium
• If buoyant force > mg, object will accelerate upwards
• If buoyant force < mg, object will accelerate downwards

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28
Q

What happens if we submerge an object with the same volume and mass as the fluid displaced?

A
  • Then the buoyant force will equal the force of gravity of the object and the object will be in static equilibrium
  • mg=buoyant force
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29
Q

What happens if we submerge an object with the same volume but a higher mass as the fluid displaced

A

Then the buoyant force will be less than the force of gravity and the object will accelerate downward.
• mg>buoyant force

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30
Q

What happens if we submerge an object with the same volume but lower mass as the fluid displaced

A

Then the buoyant force will be greater than the force of gravity and the object will accelerate upward.
• mg

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31
Q

Density

A

P = Mass / Volume

- if something is more dense than water then it will sink and if it is less dense then it will float

32
Q

The Center of Gravity in Regard to Buoyancy

A 
• The force of gravity acts through the
center of gravity
• Related to body orientation and
distribution of mass
• Density of different tissues

• The buoyant force acts through
the center of volume.

  • That is different parts of the body
    have different density where volume
    is just how much space each limb
    takes up.
33
Q

3 things dynamic fluid is proportional to

A
  1. the density of the fluid
  2. the surface area of the object immersed in the fluid
  3. The relative velocity of the object to the fluid
    (squared).
    • Relative velocity is the difference between the object’s velocity and the fluids velocity.
    Therefore relative velocity is the most important factor
    in determining dynamic fluid forces.
34
Q

Drag Force

A

Drag is the component of the dynamic fluid force that
opposes (parallel but opposite in direction) the relative
motion of the object with respect to the fluid.

• A force exert on the object by the fluid molecules.

35
Q

2 Types of Drag

A

• Surface drag is the sum (adding up all) of the friction
forces acting between the fluid molecules and the
surface of the object.

• Form drag is a result of how fluid molecules travel
around an object due to the objects shape.

36
Q

Surface Drag

A

Surface drag is also called Skin friction or viscous drag

• As a molecule slides past the surface of an object, the
friction between the surface of the object and the
molecules in the fluid creates a layer of molecules
called the boundary layer

• The surface drag is due to the boundary layer of
molecules that come in contact with the object and
“rub up against” the object

37
Q

4 Factors of Surface Drag

A
  1. Coefficient of drag (similar to friction)
    • Coefficient of drag is affected by the roughness of the
    surface and viscosity of the fluid
    • Shaving, bodysuits.
  2. Density of the fluid
  3. Cross sectional area of the object
  4. Relative velocity (squared)
    • How quickly the object and the surface are moving.
38
Q

Form Drag

A

Fluid traveling around any fairly smooth object will travel in a path called laminar flow

  • Laminar flow is when the fluid molecules diverges at the point of contact of the object and then converge after the object has passed (also called a wake)
  • The amount of divergence depends on the shape of the object and the convergence is a result of the natural flow of the fluid to rebalance pressure
39
Q

What happens in front and behind of an object (Form Drag

A

• The imbalance in pressure opposes forward motion

• In front the high pressure produces a force to slow the
object down.

  • Collision and divergences of molecules
  • Behind the object the low pressure “pulls” the object back.
  • Convergence of molecules to regain pressure
40
Q

Shape that minimizes form drag

A
  • The shape of an object that minimizes form drag is one that
  • minimizes the change in direction of the molecules first in contact with the object
  • takes up the space where the turbulent flow or vacuum would occur behind the object.
  • cuts through the air or fluid
  • slowly allows the fluid to reestablish it’s original trajectory
41
Q

5 Factors of Form Drag

A
  1. Shape of the object
  2. Drag coefficient
  3. Density of the fluid
  4. Cross sectional area of the object
  5. Relative velocity (squared)
42
Q

Managing Drag in Sprot

A
  • Make body or clothing smoother (fast-skin bodysuit)
  • Streamline the shape of the body or equipment
  • Body position
  • Reduce relative velocity by drafting (sit in the vacuum, tailgating)
43
Q

DIMPLES - why are they good? Who knows

A
  • The dimples on a golf ball create tiny pockets of turbulence. This causes a small turbulent layer around the ball which holds the fluid molecules close to the ball. Because of this the turbulent wake behind the ball is diminished
  • Therefore dimpling diminishes the form drag by changing the laminar flow.
44
Q

Lift Force

A

Lift force is the dynamic fluid force component that acts
perpendicular to the relative motion of the object with
respect to the fluid.

  • The effect of the lift force is to change the direction of the relative motion of the object through the fluid.
  • Lift force direction is determined by the direction of flow of the fluid.
45
Q

What Causes Lift Force (molecules)

A

Lift force is caused by the lateral deflection of fluid molecules as they pass the object

  • The object exerts a lateral force on the molecules and the molecules exert an equal but opposite lateral force on the object that causes lift.
  • Lift force is proportional to the lateral acceleration of the fluid molecules and the mass of the molecules that are deflected.
  • The shape and orientation of the object can modify the effect of the lift force.
46
Q

Magnus Effect

A

The way the spin of a ball effects the trajectory of the balls path

For an object with topspin,
• the molecules on the top will slow
down due to friction
• those on the bottom will not slow
down. 
For an object with backspin,
• the molecules on the bottom will slow
down due to friction
• those on the top will not slow down.
• Therefore there will be greater
pressure on the bottom of the ball
compared to the top of the ball.
• The ball will have a net upward force
47
Q

Bernoulli’s Principle

A

Faster moving fluids exert less pressure than do slower moving fluids

• If a ball is spinning in the
same direction as the fluid
there will be a decrease in
pressure

• If a ball is spinning in the
opposite direction as the
fluid there will be an
increase in pressure

48
Q

GAIT

A

– Gait is the pattern of movement of the limbs of
animals, including humans, during locomotion over a
solid substrate.

– Most animals use a variety of gaits, selecting gait
based on speed, terrain, the need to maneuver, and
energetic efficiency
• Walking
• Running
• Sprinting
• crawling

49
Q

Normal Human Gait Maintains…. (3)

A

– weight-bearing stability,
– conserving energy, and
– absorbing the shock of floor impact.

50
Q

Why do we Measure Gait

A
  1. To find out how we walk
    – What is normal and why?
    – Evaluate the Function of walking
2. To use walking as a baseline measure to
understand differences between;
– Healthy and unhealthy populations
– Ages
– Genders
– Races
51
Q

What does Gait Analysis Involve the Measure Of?

A

Kinematics, Kinetics and Electromyography

52
Q

Electromyography

A

a technique for evaluating and recording the electrical activity produced by skeletal muscles

53
Q

How is Kinematics measured for GAIT (2 marker systems)

A

Passive Marker Systems use reflective markers and multiple cameras

Multiple cameras are necessary to ensure that we can digitize each marker and determine its 3 dimensional location… From the 3D digitized markers we can derive the joint kinematics

Active Marker Systems are similar to the passive marker system but use “active” markers. The markers are triggered to illuminate.

Electromagnetic Systems track the position (X, Y, and Z
Cartesian coordinates) and orientation of small sensors

• Accelerometers, gyroscopes and magnetometers can also be used to capture motion

54
Q

Electrical Goniometers (GAIT Kinematics)

A

– An electrical device for measuring joint angles
– They are simple to use and are relatively inexpensive
compared to motion capture systems

55
Q

How is Kinetics recorded for GAIT

A

Pressure mats and insoles can help us to
determine a basic estimate of force and center
of pressure movement

Force plates embedded in floors or treadmills can
give us the most detailed information about contact kinetics

56
Q

Inverse Dynamics

A

Combining the Kinematic and Kinetics can allows us to calculate joint forces, torques and muscle forces

57
Q

4 Steps in a Gait

A 
Initial Contact 
---Loading Response
Midstance
Toe Off
Swing
58
Q

Initial Contact of GAIT

A

(0%) - Instantaneous point when leading foot touches the ground.
•preparation for loading response
•Heel strike or heel contact

59
Q

Midstance of GAIT

A

(10-30%) - Body weight transferred onto stance
limb.
•contralateral foot leaves the ground (OT) and body weight travels along the length of the foot until aligned over the forefoot.
•descending initial peak of the vertical force graph
•first half of single support

60
Q

Loading Response of GAIT

A 
0 -10%
•Body weight transferred onto stance
limb.
•Foot in full contact with floor
•Ascending peak of the vertical force
•initial double-limb support
61
Q

Terminal Stance of GAIT

A

30-50%
•begins with heel rise (HR), ends when opposite foot contacts the ground (OI).
•body weight moves ahead of forefoot.
•Heel off (HO) when the heel leaves the ground.
•Ascending second peak of vertical force
•second half of single-limb support.

62
Q

Preswing of GAIT

A 
50-60%
•It begins with opposite foot contact,
ends with ipsilateral toe off (TO).
•stance limb unloaded and body weight
transferred onto opposite limb.
•Descending 2nd peak of the vertical force
• terminal double-limb support
63
Q

Terminal Contact of GAIT

A
  • instant when foot leaves the ground.

* end of stance, beginning of swing.

64
Q

Initial Contact

A

60-70%
It begins the moment the foot leaves the ground and continues until maximum knee flexion occurs when the swinging extremity is directly under the body and directly opposite the stance limb.

65
Q

Midswing

A

70-80%
begins following maximum knee flexion and ends when the tibia is in a vertical position. continued limb advancement and foot clearance.

66
Q

Terminal Swing

A

85-100% (last 15% of the gait cycle)
The tibia passes beyond perpendicular,
and the knee fully extends in preparation
for heel contact.

67
Q

5 Steps in the Stance Phase of GAIT

A 
Initial Contact
Loading Response
Mid Stance
Terminal Stance
Preswing
68
Q

3 Steps in the Swing Phase of GAIT

A

Initial Swing
Midswing
Terminal Swing

69
Q

Composition of GAIT Cycle (%’s)

A

62% stance phase and 38% swing phase

two periods of double stance that occupy 25% of the gait cycle

70
Q

Each of the muscles involved in GAIT

A

Glutes-hip extension during loading response
Quads-knee extension during loading response
Calves-ankle plantarflexion during heel rise in terminal
stance
Illiopsoas-hip flexion during pre and initial swing
Hamstrings-hip extension to decelerate limb during
terminal swing
TA-ankle dorsiflexion during swing phase to allow foot
clearance and during loading response to maintain foot
position
Hip- changes from ext to flex just before TO
Knee-changes from max flex to ext during swing
Ankle – changes from plantar to dorsi just after TO

71
Q

Center or Pressure (GAIT)

A

the instantaneous point of application of the ground reaction force

Measuring foot centre of pressure movement during walking can tell us about the point of

Application of the GRF vector and how we use our feet while walking (Recall inversion / eversion how force travels along the foot)

72
Q

3 Functional Tasks of Walking Theory

A

The first functional task is weight acceptance.
– The demand for immediate transfer of body weight onto the limb as soon as
it contacts the ground requires;
• initial limb stability
• shock absorption
• momentum of progression preservation.

• The second functional task is single- limb support.
– During this period, the total body weight is exclusively supported on the
stance limb.
• Forward progression while maintaining stability.

• The third functional task is limb advancement.
– The stance limb leaves the ground and advances forward to posture itself in
preparation for the next initial contact.

73
Q

Double Pendulum Analogy (GAIT)

A

That is, during single limb support the body (CofG) vaults over the extended limb with minimal energy expenditure

• During double limb support there is a redirection of the whole body (CofG) over the other extended limb and the inverted pendulum continues on the other side.

• Therefore the only major energy expenditure is during the
redirection portion.

74
Q

The 6 Determinants of GAIT (what allows us to minimize unnecessary movement of the COG?)

A

– 1. Pelvic rotation - if pelvis did not rotate, the whole stride length would come from hip flex. hip ex. Vert pelv rotation reduces angle of hip flex extend which reduces vert movement of hip.

– 2. Pelvic Obliquity - vert movement of trunk is less than that of the hip d/t pelvic tilt about an anteroposterior axis.

– 3. Knee flexion in stance phase - stance phase knee flexion shortens the leg in midstance

– 4. Ankle Mechanism - backward projection of the ankle lengthens leg

– 5. Foot Mechanism - so does forward projection of the forefoot during preswing

– 6. Lateral Displacement of body - if feet are far apart then large side to side movements would be necessary to maintain balance, having them closer reduces the size of these movements.

75
Q

Gait measures between individuals

A

• Changes in swing stance ratio
– If step length is too short there may be an underlying abnormality
– inadequate push-off/pull-off, pain.

• Left/right Asymmetry

EPHE 201 - Qual Analysis (3 decks)

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