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Bio 3 Flashcards

1
Q

What is inertia

A

An objects resistance to changes in its state of motion

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2
Q

What is the one thing inertia depends on

A

Mass

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3
Q

An object with greater mass is more ________ to speed up, slow down, or change direction while moving linearly

A

Difficult

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4
Q

What does angular inertia depend on

A

Mass and distribution of mass relative to the axis of rotation

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5
Q

Moment of inertia symbol and unit

A

I
Kgm2

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6
Q

Radius of gyration symbol and unit

A

k
m

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7
Q

What is radius of gyration

A

Distance between axis of rotation and point at which an objects mass could be concentrated to keep the same angular inertia as the object had in to original shape

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8
Q

What are newtons laws of motion (angular version)

A
  1. A rigid object will remain in its current state of angular motion unless a net external moment is applied
  2. The change in angular motion (angular acceleration) of an object is directly proportional to the net momentum acting on the object, and inversely proportional to the objects momentum of inertia
  3. For every action there’s an equal and opposite rxn
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9
Q

Explain “a rigid object will remain in its current state of angular motion unless a net external momentum is applied”

A

-The object will not rotate if it was not rotating to begin with
-The object will continue rotating at a constant angular velocity if it was already rotating

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10
Q

What is momentum

A

The quantity of motion that a body/object has

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11
Q

Angular momentum symbol and units

A

H
Kgm2/s

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12
Q

T or F: in human movement, the moment of inertia is not always constant

A

T
-it can change as we alter the configuration of body segments

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13
Q

As moment of inertia increases, does angular velocity increase or decrease

A

Decreases

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14
Q

Give an example of moment of inertia increasing as angular velocity decreases

A

Charlottes turns w arms in=faster/more rotation

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15
Q

Why does a sphere accelerate faster than a ring

A

The sphere has the lowest radius of gyration (k) and moment of inertia (I)

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16
Q

Law of action rxn examples

A

Knee extension:
Vastus mm produce equal and opposite moments on the shank and thigh

Falling forward:
Circle arms forward to create a moment in the CCW direction creating a CW moment at the trunk

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17
Q

What is deformable bodies

A

Considers deformation when force is applied

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18
Q

Two types of forces

A

Internal and external

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19
Q

Internal forces

A

Act within system of interest
-holds musculoskeletal system together
-can result from external forces

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20
Q

External forces

A

Act on the system as a result of its interaction w surrounding environment
-affect internal structures

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21
Q

Why is it important to understand the mechanical properties of tissues and how they respond to forces

A
  • evaluating injury mechanisms
  • preventing injury
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22
Q

Unit for stress

A

Pa

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23
Q

What is axial direction

A

Tension/compression; stress acts perpendicular to analysis plane

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24
Q

What is transverse direction

A

Shear; stress acts parallel to analysis plane

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25
What 3 types of stresses represent the principal stresses
Tensile Compressive Shear
26
What is tension (tensile stress)
Stress due to a force that pulls apart the molecules bonding the object together -forces act perpendicular to analysis plane -tensions causes the object to stretch in the direction of the external force
27
Example of tension (tensile stress)
Hanging from a bar -sprain, mm tears, dislocation
28
Compression (compressive stress)
Stress due to a force that pushes molecules of an object more tightly together -forces act perpendicular to analysis plane - compression tends to cause the object to shorten in the direction of the external force
29
Example of compression (compressive stress)
Push up Bruising, crush fractures
30
Shear stress
Stress due to forces acting parallel to analysis plane -slides molecules of the object past each other -changes the orientation of the sides of the object
31
Example of shear stress
Rug burn -blistering, dislocations, shear fractures
32
Real life loading situations in the human body commonly involve what
-multiple stresses at the analysis plane -varying stresses across the analysis plane
33
What is bending & example
A combo of tension and compression causing an object to deflect in a curved shape -trying to break a pencil *stress would be applies in the middle
34
What 3 things allow bones to withstand different types of loading situations
1. Round in cross section 2. More dense near perimeter 3. Less dense near neutral axis
35
What is torsion & example
Shear stresses acting in opposite directions causing object to deform by twisting Ex: twisting ends of pencil in opposite directions
36
Combined loads is when…
Tension, compression, shear, bending, and torsion are combined
37
What is strain
Deformation in an object in response to loading, relative to its original length
38
Linear strain
Produced by compressive or tensile stresses
39
Shear strain
Produced by shear stresses
40
External forces —> resisted by internal forces —> ?
Quantified by mechanical stress
41
External forces —> deformation —> ?
Quantified by mechanical strain
42
What are the two ways in which deformation is measured
Absolute terms Relative terms
43
Absolute terms
Change in length between original and deformed length
44
Relative terms
Referred to as strain - change in length between l0 and l relative to l0
45
Are compression & tension + or -
Tension is + Compression is -
46
Deformable objects loaded in tension stretch and compress in what directions
- stretch in axial direction - compress in the transverse direction
47
Deformable objects loaded in compression and example
- Shorten in axial direction - stretch in transverse direction Ex: intervertebral disk
48
For strain: Axial direction is __________ of the applied load Transverse direction is ________ to the applied load
In the direction Perpendicular
49
Poissons ratio
Relationship between strains in transverse direction and axial direction
50
What is elastic behaviour
When the stress strain curve is linear -stretch increases proportionally to strain -object stretches under a tensile force or shortens under a compressive force -object returns to original shape when the force is removed
51
What is young's modulus and what is its symbol and unit
Relationship between stress and strain for a material E Pa
52
If a material has a higher elastic modulus it means that…
Material is stiffer -steeper slope of stress strain curve
53
If a material has lower elastic modulus it means that…
Material is more pliant -shallower slope of stress strain curve
54
T or F: when a force exceeds a certain size, there will be permanent deformation
T
55
Plastic behaviour
When the stress strain curve becomes non linear (curved)
56
Yield point/elastic limit
Point at which further stress will cause plastic deformation -object won’t return to original shape when load is removed
57
Material strength
Max stress or strain a material can withstand before failure
58
Yield strength
Stress at the elastic limit of the stress strain curve -occurs at end of elastic region -stresses beyond this point cause deformation
59
Ultimate strength
Max stress the material can withstand -stress at the highest point of the stress strain curve
60
Failure strength
Stress where breakage/rupture occurs -occurs at end point of stress strain curve
61
Failure strain
Strain in a material when breakage/rupture occurs -occurs at endpoint of stress strain curve
62
Toughness
Ability of a material to absorb energy - more energy is needed to break a tougher material -represented by the area under the stress strain curve
63
What is tissue composed of
Ground substance Water Minerals Collagen (stiff, high tensile strength) Elastin ( pliant and extensible)
64
Isotropic
Same mechanical properties in every direction
65
Anisotropic
Different mechanical properties depending on the direction of the force
66
What can bone withstand
Compression Tension Shear
67
Mechanical strength and stiffness is affected by what
Rate of loading -stronger and stiffer if loaded fast -weaker and less stiff if loaded slowly
68
What can articulate cartilage withstand
Compression Tension Shear
69
When cartilage is subjected to compressive forces, it exudes water which leads to what
-creep - stress relaxation
70
What is creep
Tissue loaded at a constant stress
71
What is stress relaxation
Tissue is loaded at a constant strain
72
Tendon and ligament characteristics
-high in tensile strength -little resistance in compression or shear - exhibit creep and stress relaxation - stretch easily under low tensile stresses - become more stiff under high tensile stresses

Biomechanics (2 decks)

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