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# Kinetics 2009 Lecture 2with Torque Joke Not To Post

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• Forces are vector quantities - have direction and magnitude Physical Movement - velocity, acceleration, deceleration Weight (both mass and pull of gravity) - pounds, Newtons Force - pounds, Newtons Stress - pascal Friction - Work Arrows indicate vectors - #’s usually accompany vectors showing amount of force. Vectors can be added or subtracted if working in the same line Rugby scrum – Five Guys pushing – 70/60/30/40/50 against four guys 100/75/75/75 250 against 325 - four guys win
• Magnitude – length of vector indicates “size” Direction – which way it is acting Sense – is it positive (muscle) or negative (resistance) Point of Application – Where it is acting
• Example: Movement of arms, legs is rotatory A B
• Example: Draw rectangle on board 3 by 4 with internal line 5 3 N 4 N 5 N
• Demonstrate with levers
• Torque is an expression of effectiveness of a force in turning a lever system. Such as opening a car door Using a lever to lift something - longer the force arm less force needed – demonstrate with levers (Aristotle moving the Earth) Clinical application - passive stretching - demonstrate with elbow extension points at wrist and midway to elbow
• Demonstrate with lever and fulcrum. In balance - forces and force arms equal Or in other words if equal weight on each side Think of a see saw -can adjust length of arms
• Demonstrate - have fulcrum at one end, resistance in middle and use “fish scale” to show force used Brachioradialis origin – proximal 2/3 of the lateral supracondylar ridge of the humerus and lateral intermuscular septum Inserts - lateral side of the base of the styloid process of the radius
• Demonstrate again with the force applied in the middle of the lever. Is more force required if the lever is longer and the resistance further away?
• Demonstrate with different lengths of the force arms and resistance arms, to maintain equilibrium. Do calculations - see examples from past. Go back to type of levers 1 st class show amount of force with one pound on one end 2 nd class – resistance is closer to the fulcrum RA – 1ft. FA – 2ft. Resistance is 1# RA x R = FA x F 1 x 1 = 2 x (answer is .5 #) 3 rd class – force closer to fulcrum R equal 1# RA - 2 ft. FA – 1ft RA x R = FA x F 2 x 1 = 1 x (answer is 2#)
• Demonstrate with lever and fulcrum - 1 st class lever (R1A x R1) + (R2A x R2) = FA x F (9 x 1) + (3 x 1) = 3 x (answer or Y) 12 = 3 x (Y) or answer is 4 #
• Demonstrate with lever and fulcrum 1 st class lever (R1A x R1) + (R2A x R2) = FA x F (5 x 1) + (3 x 1) = 4 x (answer or F) 8 = 4 x (F) or answer is 2 #
• Second class lever – (RA x R) = FA x F (9 x 6) = 18 x (answer or F) 54 = 18 x (F) or answer is 3 # MA = FA/RA MA = 18/9 or 2
• Second class lever – (RA x R) = FA x F (5 x 3) = 5 x (answer or F) 15 = 5 x (Y) or answer is 3 # MA = FA/RA MA = 5/3 or 1.67
• Third class lever – (RA x R) = FA x F (10 x 5) = 5 x (answer or F) 50 = 5 x (F) or answer is 10# MA = FA/RA MA = 5/10 or 0.5
• Third class lever – (RA x R) = FA x F (6 x 2) = 2 x (answer or F) 12 = 2 x (F) or answer is 6 # MA = FA/RA MA = 2/4 or 0.5
• Example in Brunnstrom - page 36 torque changes for external force – Example is Brunnstrom page 36 picture lifting weight - moment arm is essentially the resistance arm closer to the body less force a person is lifting. -- Overhead # 2 Moment Arm - exists for a moment - Overhead # 3 Example page 62 for internal force or force of muscle - Overhead # 4 Page 73 and 77 of Roberts
• ### Kinetics 2009 Lecture 2with Torque Joke Not To Post

1. 1. <ul><li>What movement (or what position) is occurring in the right knee? </li></ul>
2. 2. <ul><li>What surface term can be used to describe what you can see of the hand in this photo? </li></ul>
3. 3. <ul><li>When performing the movement in the picture the head has moved: </li></ul><ul><li>A.) Anterior </li></ul><ul><li>B.) Medial </li></ul><ul><li>C.) Posterior </li></ul>
4. 4. Kinetics Study of Forces Associated with Movement
5. 5. Scalar Quantities <ul><li>Can be measured by an instrument of scale; they are static (no direction). Has magnitude only. </li></ul><ul><ul><li>Time </li></ul></ul><ul><ul><li>Space </li></ul></ul><ul><ul><li>Mass </li></ul></ul><ul><ul><li>Speed </li></ul></ul><ul><ul><li>Temperature </li></ul></ul>
6. 6. Vector Quantities <ul><li>Indicate movement; can be measured only at a specific point in time as it is constantly changing </li></ul><ul><ul><li>1) magnitude </li></ul></ul><ul><ul><li>2) direction </li></ul></ul>
7. 7. Tug of War 500 N 200 N 100 N 400 N 300 N
8. 8. Factors to Describe Vectors <ul><li>Magnitude </li></ul><ul><li>Direction- </li></ul><ul><ul><ul><li>Vertical=Y </li></ul></ul></ul><ul><ul><ul><li>Horizontal=X </li></ul></ul></ul><ul><li>Sense/Polarity </li></ul><ul><ul><li>Internal force=positive Y </li></ul></ul><ul><ul><li>External force=negative Y </li></ul></ul><ul><li>Point of Application- Where muscle inserts to origin </li></ul>
9. 9. Types of Motion <ul><li>Translation or Linear - object moves in a straight line - all points of the object move in the same direction at the same speed, distance, and time </li></ul><ul><li>Rotation (Axial, or angular) - One point of the object is fixed and the remainder of the object moves in an arc around a fixed point. </li></ul>
10. 10. Resolution of Forces <ul><li>May have two forces acting in different directions in the same plane - can determine force by using the Pythagorean theorem. </li></ul><ul><ul><li>a(squared) + b(squared) = c(squared) </li></ul></ul>
11. 11. Resolution of Forces: Clinical Application 3 N 4 N
12. 12. Lever System <ul><li>Lever - rigid bar or structure that turns around a fixed point; representing the bones of the body </li></ul><ul><li>Fulcrum – fixed point around which rest of bar moves; representing a joint axis </li></ul><ul><li>Force - usually representative of a muscle </li></ul><ul><li>Resistance - force that must be overcome by a muscle </li></ul>
13. 13. Lever Arms <ul><li>Force - labeled F </li></ul><ul><li>Resistance - labeled R </li></ul><ul><li>Force Arm - distance between the application of force and the fulcrum - labeled FA </li></ul><ul><li>Resistance Arm - distance between the point of resistance and the fulcrum - labeled RA </li></ul>
14. 14. Torque <ul><li>Torque considered a rotary equivalent to a force </li></ul><ul><li>Produced by levers - moves around a fixed point - the rotation makes an arc or circle </li></ul><ul><li>Torque = Force x Force Arm or Resistance x Resistance Arm </li></ul><ul><ul><li>measured in newton-meters or foot-pounds </li></ul></ul>
15. 15. First Class Lever <ul><li>Fulcrum is between the force and the resistance (e.g. see saw) </li></ul><ul><ul><li>Example is atlanto-occipital joint (head and neck) </li></ul></ul><ul><ul><li>Articulation is of the occipital condyles and superior facets of C1 </li></ul></ul>
16. 16. First Class Lever F R RA FA
17. 17. 1 st Class Lever
18. 18. 1 st Class Leverhttp://video.google.com/videoplay?docid=-1013712987391348587&ei=y0KUSuyeM5qIqQLfvsy7Dg&q=atlanto+occipital+joint&hl=en
19. 19. Second Class Lever <ul><li>Force and resistance are on the same side of the fulcrum with the resistance between the fulcrum and the force (e.g. bottle opener) </li></ul><ul><ul><li>Example is foot (standing on toes) </li></ul></ul>
20. 20. Second Class Lever F R RA FA
21. 21. 2 nd Class Lever
22. 22. 2 nd Class Lever
23. 23. Third Class Lever <ul><li>Force and resistance are on the same side of the fulcrum with the force between the fulcrum and the resistance (most levers in the body are third class levers). </li></ul>
24. 24. Third Class Lever F R RA FA
25. 25. 3 rd Class Lever
26. 26. Match <ul><li>1 st class lever </li></ul><ul><li>2 nd class lever </li></ul><ul><li>3 rd class lever </li></ul><ul><li>Fulcrum in the middle </li></ul><ul><li>Force in the middle </li></ul><ul><li>Fulcrum in the middle </li></ul>
27. 27. Mechanical Advantage <ul><li>Efficiency of a lever - efficient when a small force required to overcome a large resistance. </li></ul><ul><ul><li>MA=FA divided by RA </li></ul></ul><ul><ul><li>Force Arm is greater than resistance arm then MA is greater than 1 </li></ul></ul><ul><ul><li>In third class levers, MA is always less than 1 </li></ul></ul>
28. 28. Mechanical Advantage <ul><li>If mechanical advantage is greater than one, then lever was built for force </li></ul><ul><li>If mechanical advantage is less than one, then lever was built for speed. </li></ul>
29. 29. Law of the Lever <ul><li>Lever is in equilibrium and will not move if: F x FA = R x RA </li></ul>
30. 30. What class lever is this? What downward force must be exerted at F to balance the downward torques of R1 and R2? 1' 2' 9 lbs. 1 lbs. 3' R1 F R2
31. 31. What class lever is this? What downward force must be exerted at F to balance the downward torques of R1 and R2? 1' 2' 5 lbs. 1 lbs. 4' F R1 R2
32. 32. What class lever is this? What upward force must be exerted at F to balance the downward torque of R? What is the mechanical advantage of this lever? 9' 9' 6 lbs. F R
33. 33. What class lever is this? What upward force must be exerted at F to balance the downward torque of R? What is the mechanical advantage of this lever? 3' 2' 5 lbs. F R
34. 34. What class lever is this? What upward force must be exerted at F to balance the downward torque of R? What is the mechanical advantage of this lever? 5' 5' 5 lbs. F R
35. 35. What class lever is this? What upward force must be exerted at F to balance the downward torque of R? What is the mechanical advantage of this lever? 2' 4' 2 lbs. F R
36. 36. Two Types of Musculoskeletal Torque <ul><li>External </li></ul><ul><ul><li>Forces outside the body </li></ul></ul><ul><li>Internal </li></ul><ul><ul><li>Produced by muscles, tendons, and other soft tissue in the body </li></ul></ul>
37. 37. Types of Musculoskeletal Torque
38. 38. Moment Arm <ul><li>Is the radius of the specific arc of motion. </li></ul><ul><li>This line runs perpendicular from the line of force to the axis of rotation </li></ul><ul><li>The moment arm or torque arm changes as the muscles contract and lengthen </li></ul>
39. 39. Changing Resistance Arms
40. 40. External Torque (Barbell)
41. 41. External Torque <ul><li>IF </li></ul><ul><li>Sin A = a/c </li></ul><ul><li>Sin 30 degrees = a/.3m </li></ul><ul><li>Find A </li></ul><ul><li>Moment Arm = </li></ul>
42. 42. External Torque <ul><li>Here it is! </li></ul>
43. 43. Internal Torque (Biceps)
44. 44. Internal Torque
45. 45. Moment Arm
46. 46. Internal and external Torque <ul><li>External torque will change throughout the range of motion as the length of the moment arm changes. </li></ul><ul><li>Internal torque changes throughout the range of motion as the length of the moment arm changes! </li></ul><ul><ul><li>Internal torque usually operates in response to external torque and is affected by those changes. </li></ul></ul>
47. 47. Muscle Contraction <ul><li>Defined - development of tension in the muscle </li></ul>
48. 48. Contraction versus Contracture <ul><li>A contraction is an action of the muscle </li></ul><ul><li>A contracture is a pathological process where soft tissue has become physically shorter and restricts movement </li></ul>
49. 49. Isometric Contraction <ul><li>Development of tension in the muscle, however, no movement; Length of the muscle does not change and there is no movement at a joint </li></ul><ul><li>Also know as a static contraction </li></ul>
50. 50. Isotonic Contraction <ul><li>Length of the muscle changes </li></ul><ul><li>There is joint movement </li></ul>
51. 51. Types of Isotonic Contractions <ul><li>Concentric - is a shortening contraction; Length of the muscle shortens; Force is greater than the resistance </li></ul><ul><li>Eccentric - length of the muscle lengthens; Also called a lengthening contraction; Resistance is greater than force </li></ul>
52. 52. Concentric Contraction
53. 53. Eccentric Contraction
54. 54. Forces on Musculoskeletal System