1. 4 FUNCTIONS of MACHINES 1. Balance 2 or more Forces 2. Force advantage 3. Linear ROM and/or Speed 4. Change direction of F motive

2. 3 Components of Levers 1. Axis or fulcrum 2. Motive Force 3. Resistive Force

3. PROPERTIES OF A FORCE 1. Magnitude 2. Direction 3. Point of Application 4. Line of Action

4. No Torque Net Torque No FA example Fig 4.3d No FA example Fig 4.3d Imbalance of Tm & Tr resultant motion in the direction of the greatest Torque T motive = T resistive T motive = T resistive

5. FA resistive action line of gravity acting through lower arm’s c of g to axis of rotation (elbow joint) FA motive action line of muscle pulling on bone to axis of rotation (elbow joint)

6. Figure 4.4 on page 149  4.4a T motive = T resistive  result is no motion  4.4b T motive > T resistive  resultant motion is ccw  4.4c T motive < T resistive  resultant motion is cw

7. Figure 4.6 - Question 2 page 151 if A = 100 weight units d must = 1.0 distance units if A = 100 weight units d must = 1.0 distance units if A = 40 weight units d must = 2.5 distance units if A = 40 weight units d must = 2.5 distance units

8. Resultant Torque Vector  Resultant Arrow represents Magnitude & Direction  Resultant comprised of 2 components: 1. Ro = vertical/perpendicular component 2. Stabl or Disl = horizontal/parallel component

9. Position 1 more Stabl than Ro Position 2 100% Ro Position 3 more Disl than Ro Figure 4.8 on page 154

10. Figure 4.10 on page 156  F 1 = Stabl (pulls toward axis/joint)  FA for F 1 =  d from axis to F 1  F 2 = 100% Ro (no horz component)  FA for F 2 =  d from axis to F 2  F 3 = Disl (pulls away from axis/joint)  FA for F 3 =  d from axis to F 3

11. Figure 4.12b on page 157 1. Draw Resultant Motive Force Vector 2. Draw Resultant Resistive Force Vector 3. Draw Motive and Resistive FA’s

12. FIG 4.12b page 157

13. Mechanical Disadvantage Advantage FA MOTIVE < FA RESISTIVE FA MOTIVE < FA RESISTIVE LARGER F MOTIVE required to overcome SMALLER F RESISTIVE LARGER F MOTIVE required to overcome SMALLER F RESISTIVE 3rd class levers 3rd class levers FA MOTIVE > FA RESISTIVE SMALLER F MOTIVE required to overcome LARGER F RESISTIVE 1 st and 2 nd class levers

14.  Axis/Fulcrum between MF and RF  rare in human body  serves all 4 functions of machines 1 st Class Lever Fig 13.11 “Basic Biomechanics” Susan J. Hall 3 rd edition

15.  Axis at one end, F motive further away than F resisitive  FA motive > FA resisitive  only serves 1 function of machines 2 nd Class Lever Fig 13.11 “Basic Biomechanics” Susan J. Hall 3 rd edition

16.  Axis at one end, F resisitive further away than F motive  FA motive < FA resisitive  only serves 1 function of machines 3 rd Class Lever Fig 13.11 “Basic Biomechanics” Susan J. Hall 3 rd edition

17. Wheel and Axle  A machine that gives either a Force advantage OR a ROM advantage  F advantage = F motive applied to wheel  ROM advantage = F motive applied to axel  in humans most common = ROM advantage

18. Wheel and Axle