Linear Kinematics of Human Movement

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Linear Kinematics of Human Movement
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Displacement vs Distance

• Distance path of motion
• A scalar quantity
• Has magnitude but no direction
• Displacement straight line from point A to
  point B
• Pf Pi
• A vector quantity
• Has magnitude and direction
• To the right/up positive
• To the left/back negative

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Speed vs Velocity

• Speed
• Scalar
• Distance/change in time
• Velocity
• Vector
• Direction
• Direction positive positive acceleration
• Change is displacement divided by change in time
• Pf Pi/ time2 time1
• Units

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Linear Acceleration

• Rate of change in velocity
• v2 v1/ t2 t1
• v2 gt v1 incr accel positive accel
• v2 lt v1 decr accel neg accel
• v2 v1 zero acceleration
• Magnitude of acceleration
• Direction Affect on Acceleration
• Average vs instantaneous acceleration

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Kinematics of Projectile Motion
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Three mechanical purposes used in projecting
object

• For maximum horizontal distance
• Maximum vertical distance
• Maximum accuracy

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Components of a projectile vector

• Horizontal
• Vertical
• Factors influencing projectiles components
• Gravity
• Air resistance

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Factors Influencing a Projectiles Trajectory
before Release

• Angle of Projection
• Projection Acceleration
• Height of Projection

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Angle of Projection

• Trajectory solely dependent on projection angle
• Three basic shapes
• Purely vertical
• Oblique projection
• Horizontal projection

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Angle of Projection

• Trajectory solely dependent on projection angle
• Three basic shapes
• Purely vertical
• Oblique projection
• Horizontal projection
• Affects of Projection Angle

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Projection Acceleration

• Projection angle constant will determine length
  and size of trajectory
• Vertical P. angle initial acceleration
• Oblique angle acceleration determines both
  vertical and horizontal length of trajectory

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Projection Height

• Difference between height initial and height at
  which lands or ceases motion
• When projection angle and acceleration are
  constant this equates to longer flight time and gt
  horizontal displacement

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Optimal Projection Conditions

• Want to maximize accel and release height
• PH 0 then PA 45
• Increasing PH
• Decreasing PH

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Projecting Body for Vertical Distance

• Three Factors Determine Bodys Reach Height
• Vertical Velocity of COG at Takeoff
• Height of the COG at Takeoff
• COG to Finger Tip Height

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Vertical Velocity of COG at Takeoff

• Determines how high COG will travel
• Influence of air resistance
• Projection angle influences takeoff velocity
• Pure vertical vs vertical and horizontal combined

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Height of COG at Takeoff

• Must be maximized before takeoff
• COG can be moved relative to the body by
  relocating segments
• Must occur before takeoff
• How can we increase COG before takeoff?

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COG to Finger Tip Height

• Distance between COG at the peak of flight and
  the finger tips of reaching hand
• Maximize COG height at takeoff
• In air lower one arm
• Affect COG
• Gives appearance of hanging in the air
• Also increase vertical leap

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Projecting for Vertical Distance with a
Horizontal Component

• Running approach in many sports followed by a
  vertical component force
• Still have horizontal component
• Dunking a Basketball
• Angle of projection
• Large vertical velocity at takeoff
• Greatest COG at takeoff has advantage

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Projecting for Horizontal Distance

• Object projected horizontally will continue until
  ceased by external force
• Longer in the air the greater the horizontal
  component
• Tradeoff between horizontal and vertical
  component
• Horizontal Projection when takeoff and landing
  heights are equal
• Horizontal Projection when takeoff and landing
  height are unequal

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Projecting for Accuracy

• Vertical Plane Targets
• Horizontal Plane Targets
• Projecting the Body for Accuracy