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Published byCory Wiggins Modified over 6 years ago
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4 FUNCTIONS of MACHINES Balance 2 or more Forces Force advantage
Linear ROM and/or Speed Change direction of F motive
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3 Components of Levers Axis or fulcrum Motive Force Resistive Force
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PROPERTIES OF A FORCE Magnitude Direction Point of Application
Line of Action
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No Torque Net Torque Imbalance of Tm & Tr
resultant motion in the direction of the greatest Torque No FA example Fig 4.3d T motive = T resistive
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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)
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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
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Figure Question 2 page 151 if A = 100 weight units d must = 1.0 distance units if A = 40 weight units d must = 2.5 distance units
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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
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Position 1 more Stabl than Ro Position 2 100% Ro Position 3 more Disl than Ro
Figure 4.8 on page 154
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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
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Figure 4.12b on page 157 Draw Resultant Motive Force Vector
Draw Resultant Resistive Force Vector Draw Motive and Resistive FA’s
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FIG 4.12b page 157
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Mechanical Disadvantage Advantage
FAMOTIVE < FA RESISTIVE LARGER FMOTIVE required to overcome SMALLER FRESISTIVE 3rd class levers FAMOTIVE > FARESISTIVE SMALLER FMOTIVE required to overcome LARGER FRESISTIVE 1st and 2nd class levers
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1st Class Lever Axis/Fulcrum between MF and RF rare in human body
serves all 4 functions of machines
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2nd Class Lever Axis at one end, Fmotive further away than Fresisitive
FAmotive > FAresisitive only serves 1 function of machines
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3rd Class Lever Axis at one end, Fresisitive further away than Fmotive
FAmotive < FAresisitive only serves 1 function of machines
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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
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