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
2
Q
How is a forced simply defined
A
a push or a pull
3
Q
Forces cause a change in…
A
The state of motion of an object (start, stop, speed up, slow down, or change direction
4
Q
Force can either ____ or ____ an object
A
Accelerate or decelerate
5
Q
Forces come in ____
A
pairs: action and reaction
6
Q
What is magnitude
A
length of the arrow
7
Q
What is direction
A
Relative to an axis
8
Q
What is line of action
A
the shaft of the arrow
9
Q
What is point of application
A
Where it acts on an object
10
Q
What is the most familiar unit of measurement for force
A
Pound or kilopound
11
Q
What is the SI unit of measurement for force
A
Newton
12
Q
What is one N defined as
A
the force required to accelerate a 1kg mass at 1m/s^2
13
Q
1N = _____
A
(1.0kg)(1.0m/s^2)
14
Q
What is the equation for force
A
f=ma
15
Q
What are internal forces
A
forces acting within the object or system that is being studied
16
Q
Internal forces can be ____ or _____
A
compressive (pushing) or tensile (pulling)
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
18
Q
How do you measure internal forces in biomechanics
A
strain gauges into cadaver limbs to conduct testing of injury occurrence and prevention
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
20
Q
What are external forces
A
Forces that act on an object as a result of the surrounding
21
Q
What are two types of external forces
A
Contact and non-contact
22
Q
What are 3 non-contract forces
A
Gravity
magnetic
Electrical
23
Q
What type of force are air and water resistance
A
fluid contact forces
24
Q
Contact forces occur in ____
A
pairs
25
We experience gravity as ____
weight
26
Describe gravity
All objects with mass have an attraction to other objects with mass
27
What does the magnitude of attraction between items depend on
The amount of mass each object has and the distance between the two objects
28
The earth attracts someone and the person attracts the earth with ______
equal and opposite force
29
Gravity acts through our
centre of mass
30
What is your weight equal to
Your body mass in kilograms muultiplied by the acceleration due to gravity
31
What is normal force
The component of the force of the ground acting on us perpendicular to the contact surface
32
What is the normal force when we are on a surface parallel to the horizontal
equal in magnitude to the force of gravity and opposite in direction
33
What occurs to gravity and normal force when we are on a slanted surface
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
The parallel force is also called the
shear force
35
How does the parallel/shear force aact
down the slope
36
What happens to the force component on a slope
Increase in slope = increase in the magnitude of parallel force, decrease in the magnitude of perpendicular force
37
What do we need to know if order to resolve for the components of force on a slant surface
Angle of the slant
| mass of the object
38
What are the steps to resolving for the components of force on a slant surface
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
what axis is top to down
z
40
what axis in back to front
x
41
what axis is side to side
y
42
What axis are forces acting in when walking
z and x and y
43
What is used to measure external force in biomechanics
```
strain gauges
Force transducers (force plate and instrumented treadmill, pressure mats)
```
44
What are 4 types of strain gauges
- Force transducers (force plates, load cells)
- Springs
- Piezoelectric crystals
- Dynamometer
45
How do strain gauges work
An applied force will cause an object to deform and this deformation is measured and amplified by the electronics
46
What is a down size of strain gauges
expensive
47
What is used in clinical settings to measure external force
force transducers
48
What is a held dynamometer determine
- Muscle strength
| - Weaknesses
49
What is the gold standard measurement of force in biomechanics
forceplate and instrumented treadmill
50
What are the mechanics of forceplates and instrumented treadmill
Have strain gauges or force plates measuring components attached to a device to measure forces in multiple dimensions when looking at different tasks
51
What are the pros to force plates and instrumented treadmills
- accurate measure of ground reaction force
- Reliable
- Multidimensional
52
What are the cons of force plates and instrumented treadmills
- Difficult to use in the field
- Cannot measure foot pressure distribution
- Very expensive
53
What is an inexpensive alternative to measuring force
Pressure
54
What is the equation for pressure
P = F/A
55
What is pressure
The force per unit area directed perpendicular to an object surface
56
how do pressure sensors work
Most common pressure sensors measure pressure using the piezoresistive effectn
57
What is the piezoresistive effect
It is a change in the elctrical resistivity of a semiconductor or metal when mechanical strain is applied
58
What does piezo mean
to squeeze or press
59
what are the pros to pressure sensing technology?
- portable
- thin
- flexible
- lightweight
- approximation of force
- accurate for timing of foot loading
- can measure foot pressure distribution while force plates cannot
60
What are the cons to pressure sensing technology
- Unidimensional (vertical loading)
| - Degree of precision, accuracy and reliability requires testing
61
what does the unidimensionalism of pressure sensing technology mean
you can only measure in the direction that the sensor is orientated. will not measure all the component of the force
62
What is the F-Scan foot pressure mapping system? What does it do
Portable In-shoe pressure sensor. Quantifies force, contact pressure distribution, and timing. Extremely thin and high resolution
63
The foot is the ...
end point effector with the ground
64
Foot..... provides valuable insight on a variety of biomechanical variables
foot pressure distribution and timing information
65
Changes in foot landing and pressure distribution is related to...
changes in knee/hip and ankle joint angle during contact in running
66
What are changes in the joints during forefoot running
The knee is more extended, the ankle more plantarflexed and the hip in greater extension than in heel strike running at impact
67
What occurs when training in minimalist shoes
Plantar pressure starts higher in all areas and then changes to have more forefoot pressure and less heel pressure
68
How do pressure sensors compare to the gold standard in magnitude and kinematics
Well!! both have M-profile
69
What is centre of pressure
the instantaneous point of application of the ground reaction force
70
What can measuring foot centre of pressure movement during walking tell us
about the point of application of the GRP vector and how we use our feet while walking
71
how do we use our feet when walking
Work in s shape from heel to big toe
72
How do instrumented insoles and force plate compare when measuring centre pressure
match well until reaching the toe where they divert because of less sensors surrounding toe
73
How were pressure sensors used in track sports and what was found
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
how were pressure sensors used in snowboarding
to improve their skill by analyzing the dynamics of the weight distribution inside their boots. essential for identifying the weight shifting techniques
75
How do you make instrumented devices
adding force and pressure sensors to mobility devices to measure the forces that individuals produce during activity
76
In foot strike patterns what are the stages called
force development, Impact transient, peak
77
What is force developement
the slope
78
What is impact transient
the first mini peak
79
when comparing shoes on and shoes off what was found
no shoes had greater force development and had more intense impact transient
80
How does hindfoot running compare to forefoot running
forefoot running has no impact transient and decreased force development and slight increase in force development
81
does forefoot running with or without shoes have greater impact transient
without shoes
82
What are two methods to approximate internal forces
- Inverse dynamics
| - electromyography
