AS A Level Sport and Physical Education

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• AS / A Level Sport and Physical Education
• Projectiles

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PROJECTILES

• PROJECTILES
• the motion of objects in flight
• human bodies
• shot / discus / javelin / hammer
• soccer / rugby / cricket tennis / golf balls
• is governed by the forces acting
• weight
• air resistance
• Magnus effect
• aerodynamic lift
• and the direction of motion

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RELEASE
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FLIGHT
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FLIGHT

• WEIGHT
• weight will always act on a body in flight
• the amount to which weight is a predominant force
  acting governs the shape of the flight path
• if weight were the only force acting then the
  shape of the flight path would be a parabola
• some flight paths are similar to this
• shot / hammer
• human body in jumps / tumbles / dives

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AIR RESISTANCE / FLUID FRICTION

• FLUID FRICTION (or DRAG)
• this is a term applying to objects moving through
  fluids (gases or liquids)
• The force acts in the opposite direction to the
  direction of motion

• FLUID FRICTION FORCE DEPENDS ON
• the shape and size of the moving object
• the speed of the moving object
• the streamlining effect, hence
• body position and shape for swimmer
• shape of helmets for cyclists
• use of lycra clothing
• shape of sports vehicles (cars / bikes)

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FLIGHT

• RELATIVE SIZE OF FORCES
• the faster the projectile travels the greater
  will be air resistance
• aerodynamic lift applies to
• thrown objects with a wing shape profile
• javelin / discus / rugby ball / American football
  / frisbee
• the Magnus effect applies to spinning balls
• if the shapes of the flight path differ from a
  parabola then some combination of these forces
  must be relatively large compared with the weight

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FLIGHT

• LARGE AIR RESISTANCE
• example
• badminton shuttle struck hard
• the air resistance is very large compared with
  the weight
• the resultant force is very close to the air
  resistance

• later in the flight of a badminton shuttle
• now the air resistance is much less
• and comparable with the weight

• This pattern of the resultant force changing
  markedly during the flight
• predicts a markedly asymmetric path

• the shuttle would slow down rapidly over the
  first part of the flight