Mechanical Concepts

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Mechanical Concepts
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Basic terms and concepts

• Force - a push or pull has magnitude,
  , and point application
• Weight - gravitational force exerted on a body,
  measure on scale
• Torque The turning force that tends to produce
  rotation around an
• T
• Moment arm (d) the

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Mechanical loads on the body

• Compression - force.
• Tension - pulling or stretching force
• Shear - force.
• Acute Loads - a single large force
• Repetitive - repeated application of a
• .

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Loading of our tissues can produce deformation
and rupture as illustrated by a load/deformation
curve orStress/strain curve
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Mechanical loads
What is stiffness of materials?

• stress/strain in a loaded material (i.e. the
  slope on load/deformation curve also called
  ).

What is strength?

• area the curve

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Acute vs repetitive loading and the likelihood of
injury
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Levers

• Definition -
• Contains force, effort force,
  and axis (arrangement determines class of lever)
• In the body, bone is , joint is axis,
  muscle is typically effort force, segment weight
  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
• or speed and range of motion
  multiplier.

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Levers
A range of motion multiplier if the
is shorter than the resistance
arm (e.g. Force end moves cm, Resistance end
moves 10 cm)
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Levers
A force multiplier when force arm is longer (e.g.
force can lift or support a
resistance)
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Levers

• Mechanical advantage

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Is MA improved?