Kinematic and Energetic Concepts

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Kinematic andEnergetic Concepts

• Dr. Suzan Ayers
• Western Michigan University
• (thanks to Amy Gyrkos)

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Terms

• Kinematics aspects of motion w/o consideration
  of mass and force
• Kinetics effects of forces upon motions of
  material bodies
• Energetics energy and its transformations
• Motion describes displacement, velocity and
  acceleration of a body in space
• Displacement ? in bodys position between
  locations
• Velocity rate of ? in bodys displacement over
  time
• Acceleration rate of ? in bodys velocity over
  time

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• Centrifugal away from the center/axis
• Centripetal toward the center/axis
• Force measure of the amount of effort applied
• Internal force applied by one part of body on
  another part of the same body
• External force applied by another object
• Moment of force measure of the force needed to
  rotate a body around a point
• Equilibrium all points of body have velocity
• Static equilibrium all points
  velocity/acceleration0

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Quadriceps force production throughout the ROM
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• Scientific Units of Measure Highlights

• Force (F) newton (N), some kg
• 1kg9.81N
• Work (w) distance force joule (J)
• Velocity (v) km/h, m/min, m/s, /s, rad/s
• Power (P) watts (W) (forcedistance)/time spent
  moving object
• Energy (E) joule (J)
• Boxes 2.1-2.4 (p. 25)
• Table 2.4 (p. 26)

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Newtons Laws

• I. Law of Inertia
• Every object in a state of uniform motion tends
  to remain in that state of motion unless an
  external force is applied to it.
• object must overcome inertia for movement to
  occur
• Formula
• ___kg x 9.81 m/s2 ___ (force must be gt than
  this to move)
• (Body wt in lbs / 2.2 kg) i.e., 150/2.268 kg
• 68 kg x 9.81 m/s2 667.1N required to move 68 kg
• Factors influencing inertia friction, air
  resistance
• (e.g., base runner, skier)

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• II. Law of Acceleration
• Change of motion is proportionate to the force
  impressed and is made in the direction of the
  straight line in which that force is impressed.
• Objects accelerate in the direction pushed
• Formula F ma
• Mass (in kg) m, acceleration a, and applied force
  F
• Directly proportional (push 3x harder3xgt
  acceleration)
• Inversely proportional to mass (object that is 3x
  heavier moves 1/3 slower bowling ball vs.
  volleyball)
• If force or time ?, so does velocity (i.e.,
  keeping contact w/ ball longer gt time)

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• Momentum
• Product of mass velocity
• Changes as a function of mass/velocity ?s
• Velocity ? shot putter who spins faster one time
  vs another
• Mass ? swinging a heavier bat
• Short stopping time requires ? force to ?
  momentum velocity
• i.e., giving when catching a ball or landing
• Key to injury prevention

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• III. Law of Action-Reaction
• Every action has an and opposite reaction

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Energy and Power

• Kinetic energy mechanical energy due to motion
  (joule, J)
• Potential energy mechanical energy by virtue of
  height above ground (joule, J)
• Elastic strain energy stored energy in elastic
  tissues of muscles and tendons
• Power rate of doing work (aka, strength x speed)
  (joule, J)
• Positive concentric contractions produce energy
• Negative eccentric contractions absorb energy

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Points of Application

• 1) Which muscles most important in the vertical
  jump?
• Quadriceps and gluteals
• SO WHAT?!
• 2) Relative to metabolic energy consumption
• The cost associated with quiet standing is 30
  higher than resting (sitting/lying down)
• SO WHAT?!
• 3) Walking saves met energy by converting
  gravitational potential energy into forward
  kinetic energy. Running stores/re-uses elastic
  strain energy, but less efficiently than
  pendulum-like walking mechanism.
• SO WHAT?!
• Running less efficient than walking, ergo gt
  caloric cost