The document provides an overview of key topics in biomechanics including Newton's laws of motion, musculoskeletal levers, mechanical advantage, force classification systems, and vector analysis. Newton's laws describe inertia, acceleration, and action-reaction. There are three classes of levers that determine mechanical advantage. Forces can be classified as linear, concurrent, or parallel. Vector addition and resolution methods allow decomposition of forces into perpendicular and parallel components, with applications to analyzing forces in human movement.

1. Biomechanics Module
Newton’s laws
Musculoskeletal levers and mechanical advantage
Classification of force systems
Vector addition and resolution

2. Biomechanics Module
Newton’s Laws
 Law of Inertia
 Law of Acceleration
 Law of Action-Reaction
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3. Biomechanics Module
Law of Inertia (equilibrium)

3 Hall, Basic Biomechanics, 5th ed

4. Biomechanics Module
Law of Inertia (equilibrium)

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5. Biomechanics Module
Law of Acceleration

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6. Biomechanics Module
Law of Acceleration

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7. Biomechanics Module
Law of Acceleration
 
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8. Biomechanics Module
Law of Acceleration

B
10 pounds
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9. Biomechanics Module
Newton’s Laws
 Law of Inertia
Within object
 Law of Acceleration
 Law of Action-Reaction Between objects
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10. Biomechanics Module
Law of Action-Reaction
 For every action, there is an equal and opposite
reaction
 (Forces occur in pairs)
 Between two objects
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11. Biomechanics Module
Law of Action-Reaction
 For every action, there is an equal and opposite
reaction
 (Forces occur in pairs)
 Between two objects
 Objects must be in contact
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12. Biomechanics Module
Law of Action-Reaction
 For every action, there is an equal and opposite
reaction
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13. Biomechanics Module
Law of Action-Reaction
 Ground reaction force
Body
GRF = weight
13
Hall, Fig 12-1

14. Biomechanics Module
Musculoskeletal Levers
 Why is Charlie Brown up in the air?
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15. Biomechanics Module
Musculoskeletal Levers
 Why is Charlie Brown up in the air?
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16. Biomechanics Module
Musculoskeletal Levers
 (Force A)(MAA) vs (Force B)(MAB)
 Charlie Brown is up in the air if:
(Charlie’s force)(MA) < (Linus’ force)(MA)
Force A
MAA MAB
Force B
fulcrum,
pivot point
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17. Biomechanics Module
Musculoskeletal Levers
 Interaction between the forces or loads on the
segment and the joint
 Levers: two forces and a pivot point (fulcrum, axis)
 Internal force (muscle)
 External load (gravity etc)
 Pivot point (joint)
(N.B. not consistent w/ Levangie)
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18. Biomechanics Module
Musculoskeletal Levers
 First class lever
 Second class lever
 Third class lever
 Differentiated by the relative position of the internal force, external
load, and pivot point
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19. Biomechanics Module
Musculoskeletal Levers
 First class lever
Internal
force
fulcrum, pi
vot point
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20. Biomechanics Module
Musculoskeletal Levers
 Second class lever
Internal
force
fulcrum, pi
vot point
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21. Biomechanics Module
Musculoskeletal Levers
 Third class lever
Internal
force
fulcrum,
pivot point
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22. Biomechanics Module
Mechanical advantage

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23. Biomechanics Module
Mechanical advantage

First Class Lever
Ext
Ext Int
Mech Adv = 1 if
fulcrum in middle
fulcrum,
pivot point
External MA = Internal MA
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24. Biomechanics Module
Mechanical advantage

Second Class Lever
Ext Int
Mech Adv > 1
fulcrum
External MA < Internal MA
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25. Biomechanics Module
Mechanical advantage

Third Class Lever
Int Ext
Mech Adv < 1
fulcrum
External MA > Internal MA
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26. Biomechanics Module
Classification of force systems
 Linear
 same segment
 same plane
 same line
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27. Biomechanics Module
Classification of force systems
 Linear
 same segment
 same plane
 same line
 Concurrent
 same segment
 same plane
 common point of application
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28. Biomechanics Module
Classification of force systems
 Linear
 same segment
 same plane
 same line
 Concurrent
 same segment
 same plane
 common point of application
 Parallel
 same segment
 same plane
 parallel to each other
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29. Biomechanics Module
Fun with Forces
 Vector addition
 Composition
 Tip to tail
 Parallelogram
 Vector resolution
 Graphical
 Trigonometric
 Application to human movement
 Parallel forces
 Perpendicular forces
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30. Biomechanics
Vector addition
 Composition
 Works with collinear vectors
 Same direction (addition)
+ =
 Opposite direction (“subtraction”)
+ =
30
Hall, Fig 3-11, 3-12

31. Biomechanics
Vector addition
 Addition (composition)
Works with collinear vectors
31
Hall, Fig 3-11, 3-12

32. Biomechanics
Vector addition
 Addition (composition)
Works with collinear vectors
32
Hall, Fig 3-11, 3-12

33. Biomechanics
Vector Addition
 Tip to tail
 Concurrent vectors (vectors which can intersect)
+ = =
+ = =
33
Hall, Fig 3-13

34. Biomechanics
Vector addition
 Addition – tip to tail
34
Hall, Fig 3-13

35. Biomechanics
Vector addition
 Addition – tip to tail
35
Hall, Fig 3-13

36. Biomechanics
Vector Addition
 Addition – parallelogram
+ = =
+ = =
36
Hall, Fig 3-13

37. Biomechanics
Vector addition
 Addition – parallelogram
37
Hall, Fig 3-13

38. Biomechanics
Vector addition
 Addition – parallelogram
38
Hall, Fig 3-13

39. Biomechanics
Vector Resolution
 Resolving a vector into perpendicular components
 Methods:
 Graph paper
 Trigonometry
39

40. Biomechanics
Vector Resolution
 Graphically
40 Hall, Fig 3-15

41. Biomechanics
Vector Resolution
 Graphically
41 Hall, Fig 3-15

42. Biomechanics
Vector Resolution
 Graphically
42 Hall, Fig 3-15

43. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
30 0.50 0.87
30° 45 0.71 0.71
opposite
adjacent
55 0.82 0.57
60 0.87 0.5
90 1 0
60
° adjacent opposite
43
Hall, Fig 3-15

44. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
30 0.50 0.87
30° 45 0.71 0.71
opposite
adjacent
55 0.82 0.57
60 0.87 0.5
90 1 0
60°
adjacent opposite
44
Hall, Fig 3-15

45. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
30 0.50 0.87
30° 45 0.71 0.71
opposite
10
adjacent
55 0.82 0.57
8.7
60 0.87 0.5
90 1 0
60°
adjacent opposite
5.0
45
Hall, Fig 3-15

46. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
30 0.50 0.87
30° 45 0.71 0.71
opposite
adjacent
10 55 0.82 0.57
60 0.87 0.5
90 1 0
60°
adjacent opposite
46
Hall, Fig 3-15

47. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
30 0.50 0.87
30° 45 0.71 0.71
opposite
10 10
adjacent
55 0.82 0.57
8.7 8.7
60 0.87 0.5
90 1 0
60°
adjacent opposite
5.0 5.0
47
Hall, Fig 3-15

48. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
30 0.50 0.87
20sin(55) = 16.4
45 0.71 0.71
55 0.82 0.57
60 0.87 0.5
90 1 0
55
°
20cos(55) = 11.4
48
Hall, Fig 3-15

49. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
30 0.50 0.87
45°
45 0.71 0.71
55 0.82 0.57
60 0.87 0.5
90 1 0
55° 30°
Hypotenuse = 100
49
Hall, Fig 3-15

50. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
30 0.50 0.87
45°71
45 0.71 0.71
71 55 0.82 0.57
82
50 60 0.87 0.5
90 1 0
55° 57 87 30°
Hypotenuse = 100
50
Hall, Fig 3-15

51. Biomechanics
Vector Resolution
Angle Sin Cos
 Trigonometric 0 0 1
 How does angle change the composition? 30 0.50 0.87
45 0.71 0.71
55 0.82 0.57
60 0.87 0.5
90 1 0
90° 60° 45° 30° 0°
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52. Biomechanics Module
Application to human movement
 Resolve force into:
 Perpendicular force
 Rotation
 Parallel force
 Compression
 Position dependent perpendicular
parallel
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53. Biomechanics Module
End of Biomechanics Module
 Don’t forget to take the quiz
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