Mechanical Concepts

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Mechanical Concepts
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Basic terms and concepts

• Force - a push or pull has magnitude, direction,
  and point application
• Weight - gravitational force exerted on a body,
  measure on scale
• Torque The turning force that tends to produce
  rotation around an axis (an off center force)
• T Fd
• Moment arm (d) the distance from axis where
  force is applied

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Mechanical loads on the body

• Compression -
• Tension -
• Shear -
• Acute Loads -
• Repetitive -

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Load/deformation curve orStress/strain
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Mechanical loads
What is stiffness of materials?

• stress/strain in a loaded material (slope on
  load/deformation curve modulus of elasticity)

What is strength?

• area under the curve

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Acute vs repetitive loading
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Levers

• Definition - a rigid bar that rotates around an
  axis
• Contains resistance force, effort force, and axis
  (arrangement determines class of lever)
• In the body, bone is bar, joint is axis, muscle
  is typically effort force, segment weight
  objects are resistance forces

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First class levers
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2nd Class levers
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3rd class levers
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Levers

• Depending on arrangement of components, levers
  can be used for force multiplier or speed and
  range of motion multiplier
• Mechanical advantage EF moment arm/RF moment arm

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Is MA improved?