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4 FUNCTIONS of MACHINES

4 FUNCTIONS of MACHINES. Balance 2 or more Forces Force advantage Linear ROM and/or Speed Change direction of F motive. 3 Components of Levers. Axis or fulcrum Motive Force Resistive Force. PROPERTIES OF A FORCE. Magnitude Direction Point of Application Line of Action.

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4 FUNCTIONS of MACHINES

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

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

  3. PROPERTIES OF A FORCE • Magnitude • Direction • Point of Application • Line of Action

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

  5. FA resistiveaction line ofgravityacting through lower arm’s c of g to axis of rotation (elbow joint)FA motiveaction line ofmusclepulling on bone to axis of rotation (elbow joint)

  6. Figure 4.4 on page 149 • 4.4a Tmotive = Tresistive result is no motion • 4.4b Tmotive > Tresistive resultant motion is ccw • 4.4c Tmotive < Tresistive resultant motion is cw

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

  8. Resultant Torque Vector • Resultant Arrow represents Magnitude & Direction • Resultant comprised of 2 components:1. Ro = vertical/perpendicular component2. Stabl or Disl = horizontal/parallel component

  9. Position 1moreStablthan RoPosition 2100% RoPosition 3moreDislthan Ro Figure 4.8 on page 154

  10. Figure 4.10 on page 156 • F1 = Stabl (pulls toward axis/joint) • FA for F1 =  d from axis to F1 • F2 = 100% Ro (no horz component) • FA for F2 =  d from axis to F2 • F3 = Disl (pulls away from axis/joint) • FA for F3 =  d from axis to F3

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

  12. FIG 4.12b page 157

  13. FAMOTIVE < FARESISTIVE LARGERFMOTIVErequiredto overcome SMALLERFRESISTIVE 3rd class levers FAMOTIVE > FARESISTIVE SMALLERFMOTIVE required to overcome LARGER FRESISTIVE 1st and 2nd class levers MechanicalDisadvantageAdvantage

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

  15. 2nd Class Lever • Axis at one end, Fmotivefurther away than Fresisitive • FAmotive > FAresisitive • only serves 1 function of machines Fig 13.11 “Basic Biomechanics” Susan J. Hall 3rd edition

  16. 3rd Class Lever • Axis at one end, Fresisitive further away than Fmotive • FAmotive < FAresisitive • only serves 1 function of machines Fig 13.11 “Basic Biomechanics” Susan J. Hall 3rd edition

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

  18. Wheel and Axle

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