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EPHE 341 > Forces > Flashcards

Forces Flashcards

1
Q

What is biomechanics

A

The study of the effects of internal and external forces on the human body in movement and rest

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2
Q

How is a forced simply defined

A

a push or a pull

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3
Q

Forces cause a change in…

A

The state of motion of an object (start, stop, speed up, slow down, or change direction

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4
Q

Force can either ____ or ____ an object

A

Accelerate or decelerate

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5
Q

Forces come in ____

A

pairs: action and reaction

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6
Q

What is magnitude

A

length of the arrow

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7
Q

What is direction

A

Relative to an axis

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8
Q

What is line of action

A

the shaft of the arrow

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9
Q

What is point of application

A

Where it acts on an object

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10
Q

What is the most familiar unit of measurement for force

A

Pound or kilopound

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11
Q

What is the SI unit of measurement for force

A

Newton

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12
Q

What is one N defined as

A

the force required to accelerate a 1kg mass at 1m/s^2

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13
Q

1N = _____

A

(1.0kg)(1.0m/s^2)

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14
Q

What is the equation for force

A

f=ma

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15
Q

What are internal forces

A

forces acting within the object or system that is being studied

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16
Q

Internal forces can be ____ or _____

A

compressive (pushing) or tensile (pulling)

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17
Q

What are the internal forces when you land from a jump

A

A force from your lower leg on your upper leg through your knee and an equal and opposite force from your upper leg to your lower leg through your knee

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18
Q

How do you measure internal forces in biomechanics

A

strain gauges into cadaver limbs to conduct testing of injury occurrence and prevention

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19
Q

What does a strain gauge or optical fiber on human or animal tendon tell you

A

The force acting across a tendon and the anthropoemetric location of the muscle

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20
Q

What are external forces

A

Forces that act on an object as a result of the surrounding

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21
Q

What are two types of external forces

A

Contact and non-contact

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22
Q

What are 3 non-contract forces

A

Gravity
magnetic
Electrical

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23
Q

What type of force are air and water resistance

A

fluid contact forces

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24
Q

Contact forces occur in ____

A

pairs

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25
Q

We experience gravity as ____

A

weight

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26
Q

Describe gravity

A

All objects with mass have an attraction to other objects with mass

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27
Q

What does the magnitude of attraction between items depend on

A

The amount of mass each object has and the distance between the two objects

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28
Q

The earth attracts someone and the person attracts the earth with ______

A

equal and opposite force

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29
Q

Gravity acts through our

A

centre of mass

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30
Q

What is your weight equal to

A

Your body mass in kilograms muultiplied by the acceleration due to gravity

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31
Q

What is normal force

A

The component of the force of the ground acting on us perpendicular to the contact surface

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32
Q

What is the normal force when we are on a surface parallel to the horizontal

A

equal in magnitude to the force of gravity and opposite in direction

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33
Q

What occurs to gravity and normal force when we are on a slanted surface

A

The force of gravity vector still points directly towards the centre of the earth but the normal force stays perpendicular to the contact surface and is no longer equal and opposite to the magnitude and direction of the force of gravity

34
Q

The parallel force is also called the

A

shear force

35
Q

How does the parallel/shear force aact

A

down the slope

36
Q

What happens to the force component on a slope

A

Increase in slope = increase in the magnitude of parallel force, decrease in the magnitude of perpendicular force

37
Q

What do we need to know if order to resolve for the components of force on a slant surface

A

Angle of the slant

mass of the object

38
Q

What are the steps to resolving for the components of force on a slant surface

A
  1. Draw the diagram with the axis system and all known forces
  2. Solve for the magnitude of gravity (W=mg)
  3. Solve for the direction of the force of gravity relative to the axis system
  4. Solve for the parallel and perpendicular components of force
39
Q

what axis is top to down

A

z

40
Q

what axis in back to front

A

x

41
Q

what axis is side to side

A

y

42
Q

What axis are forces acting in when walking

A

z and x and y

43
Q

What is used to measure external force in biomechanics

A 
strain gauges 
Force transducers (force plate and instrumented treadmill, pressure mats)
44
Q

What are 4 types of strain gauges

A
  • Force transducers (force plates, load cells)
  • Springs
  • Piezoelectric crystals
  • Dynamometer
45
Q

How do strain gauges work

A

An applied force will cause an object to deform and this deformation is measured and amplified by the electronics

46
Q

What is a down size of strain gauges

A

expensive

47
Q

What is used in clinical settings to measure external force

A

force transducers

48
Q

What is a held dynamometer determine

A
  • Muscle strength

- Weaknesses

49
Q

What is the gold standard measurement of force in biomechanics

A

forceplate and instrumented treadmill

50
Q

What are the mechanics of forceplates and instrumented treadmill

A

Have strain gauges or force plates measuring components attached to a device to measure forces in multiple dimensions when looking at different tasks

51
Q

What are the pros to force plates and instrumented treadmills

A
  • accurate measure of ground reaction force
  • Reliable
  • Multidimensional
52
Q

What are the cons of force plates and instrumented treadmills

A
  • Difficult to use in the field
  • Cannot measure foot pressure distribution
  • Very expensive
53
Q

What is an inexpensive alternative to measuring force

A

Pressure

54
Q

What is the equation for pressure

A

P = F/A

55
Q

What is pressure

A

The force per unit area directed perpendicular to an object surface

56
Q

how do pressure sensors work

A

Most common pressure sensors measure pressure using the piezoresistive effectn

57
Q

What is the piezoresistive effect

A

It is a change in the elctrical resistivity of a semiconductor or metal when mechanical strain is applied

58
Q

What does piezo mean

A

to squeeze or press

59
Q

what are the pros to pressure sensing technology?

A
  • portable
  • thin
  • flexible
  • lightweight
  • approximation of force
  • accurate for timing of foot loading
  • can measure foot pressure distribution while force plates cannot
60
Q

What are the cons to pressure sensing technology

A
  • Unidimensional (vertical loading)

- Degree of precision, accuracy and reliability requires testing

61
Q

what does the unidimensionalism of pressure sensing technology mean

A

you can only measure in the direction that the sensor is orientated. will not measure all the component of the force

62
Q

What is the F-Scan foot pressure mapping system? What does it do

A

Portable In-shoe pressure sensor. Quantifies force, contact pressure distribution, and timing. Extremely thin and high resolution

63
Q

The foot is the …

A

end point effector with the ground

64
Q

Foot….. provides valuable insight on a variety of biomechanical variables

A

foot pressure distribution and timing information

65
Q

Changes in foot landing and pressure distribution is related to…

A

changes in knee/hip and ankle joint angle during contact in running

66
Q

What are changes in the joints during forefoot running

A

The knee is more extended, the ankle more plantarflexed and the hip in greater extension than in heel strike running at impact

67
Q

What occurs when training in minimalist shoes

A

Plantar pressure starts higher in all areas and then changes to have more forefoot pressure and less heel pressure

68
Q

How do pressure sensors compare to the gold standard in magnitude and kinematics

A

Well!! both have M-profile

69
Q

What is centre of pressure

A

the instantaneous point of application of the ground reaction force

70
Q

What can measuring foot centre of pressure movement during walking tell us

A

about the point of application of the GRP vector and how we use our feet while walking

71
Q

how do we use our feet when walking

A

Work in s shape from heel to big toe

72
Q

How do instrumented insoles and force plate compare when measuring centre pressure

A

match well until reaching the toe where they divert because of less sensors surrounding toe

73
Q

How were pressure sensors used in track sports and what was found

A

to monitor the timing and movement of the legs or the athlete. Concluded that the timing of the steps support and release phase has a great importance in performance and the pace of steps should increase towards the end of the throw event

74
Q

how were pressure sensors used in snowboarding

A

to improve their skill by analyzing the dynamics of the weight distribution inside their boots. essential for identifying the weight shifting techniques

75
Q

How do you make instrumented devices

A

adding force and pressure sensors to mobility devices to measure the forces that individuals produce during activity

76
Q

In foot strike patterns what are the stages called

A

force development, Impact transient, peak

77
Q

What is force developement

A

the slope

78
Q

What is impact transient

A

the first mini peak

79
Q

when comparing shoes on and shoes off what was found

A

no shoes had greater force development and had more intense impact transient

80
Q

How does hindfoot running compare to forefoot running

A

forefoot running has no impact transient and decreased force development and slight increase in force development

81
Q

does forefoot running with or without shoes have greater impact transient

A

without shoes

82
Q

What are two methods to approximate internal forces

A
  • Inverse dynamics

- electromyography

EPHE 341 (17 decks)

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