The Physics of Golf

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The Physics of Golf

• By Drew Thomassin

Drew Thomasson
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Types of Clubs

• Driver/Woods-Longest club, used for long
  distances, either wood, titanium or stainless
  steel
• Irons- Range from a 2 iron, less angled for
  farther distance to greater angled wedge for
  short distance
• Putter- Used for puts on the green

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Parts of the Club

• Head- Woods-wood, titanium, stainless steel
  Irons- stainless steel, titanium, iron
• Shaft- steel, carbon fiber, resin composite
• Grip- rubber or leather

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Contact with the Ball

• The contact between the club head and the ball is
  less than a thousandth of a second.
• The average force between the ball and the club
  head is around 3000 lbs, the ball becomes
  flattened against the clubface
• The ball when hit it rolls up the clubface due to
  friction and flies off with a high speed above
  the horizontal (where the clubface made contact
  with the ball)
• The momentum of the collision is conserved
  because of the high speed of the ball after the
  collision and the slowing down of the club head
  during the collision
• The collision is not elastic meaning that
  mechanical energy was lost during the collision
  when the ball flattened and rolls up clubface due
  to friction
• The clubface has grooves on it, to produce
  friction for the ball to roll up clubface and to
  produce a spin on the ball

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The D Plane

• This is a representation of perfect contact
  between the clubface and the ball
• The path which the club is moving at impact
• The normal to the clubface and the path after
  the collision
• As well as the aerodynamic lift force

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A Hook Shot

• A hook shot is when a right handed golfer makes
  first contact with the side of the ball furthest
  away from him
• A clean hit will cause the ball to spin at a
  horizontal axis
• Contact like this results in a spinning axis to
  the left causing the ball to curve to the left
• The whole D plane is shifted to the left

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A Slice Shot

• A slice shot happens when a right handed golfer
  makes first contact with the ball on the inner
  side
• Like in a hook shot this contact results in the
  ball to spin towards the right making it curve to
  the right

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History of the Golf Ball

• The feathery was the first golf ball. It was a
  leather spherical pouch filled tightly with
  feathers and then stitched. When the ball
  hardened it became very hard, then was oiled and
  painted.
• These golf balls would reach up to150 to 175
  yards
• Featheries were used until 1848 when the
  gutta-percha was invented.
• The gutta-percha is a gum from trees in
  Malaysia.
• Became roughened, people realized theyd go much
  further than smooth balls
• Modern golf ball range in theyre made of these
  days, the typical golf ball has a core made of
  polybutadiene, a type of rubber
• Harder core, farther they go
• Golf balls today can reach up to 300

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Flight of the Ball
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Diagram A

• Streamline flow still, straight airflow
• Turbulent flow- disturbed air flow
• Slow streamline air flow past smooth ball
• At a low velocity there is a thin layer of air
  near the surface of the ball called the boundary
  layer, where the speed of air is zero, as it
  extends out the air speed becomes greater in the
  streamline flow
• Air in contact with the ball is at rest relative
  to the surface of the ball
• Momentum is transferred across the boundary layer
  from the flowing air to the surface of the ball
• From A to B the boundary layer is going from high
  pressure to low pressure, the pressure difference
  helps increase velocity

Direction of Ball
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Diagram B

• Air flow at a higher speed past a smooth ball,
  showing turbulence
• From A to B streamline is similar to diagram A
• At B the turbulent wake forms
• Energy is lost, from the energy of motion
  (Kinetic Energy),
• A drag is created from the difference of
  pressures between the front and back of the ball

Direction of Ball
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Diagram C

• Turbulent flow past a dimpled ball, no spin
• The dimple surface makes the boundary layer
  turbulent
• Instead of air slowing near B, the fast moving
  air carries the turbulent boundary along with the
  ball, to extend further along the surface of the
  ball from the lower air pressure level at B to
  the higher air pressure level at C
• Drag of the dimpled ball is smaller than the
  smooth ball, less energy is dissipated in the
  smaller wake

Direction of Ball
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Diagram D

• Air flow downstream from a rotating dimpled ball,
  golf ball flight
• When hit, the ball slides up the face of the club
  due to the friction of the ridges
• The ridges cause the ball to spin on a horizontal
  axis spinning towards the golfer
• The turbulent layer is moving with the surface of
  the ball as it spins
• Air at top is moving more rapidly than air at the
  bottom, the pressure is less above the ball than
  below the ball
• A lift force is exerted perpendicularly on the
  ball
• The wake behind the ball starts lower than the
  wake of the non-spinning ball
• Ball receives a downward momentum, the ball
  recoils in upward motion

Direction off Ball
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Drag and Lift

• Depend on three variables speed of ball through
  the air, the rate of spin on the ball, surface
  texture of the ball
• Drag on the ball increases with speed through the
  air and spinning rate
• Lift increases with rate of spin at a given air
  speed and vise versa
• Different clubs vary in loft resulting in a more
  intensive spin or less intensive spin
• Clubs also vary in the power to be given to the
  ball
• Depends a lot on the club for the amount of drag
  and lift

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References

• entertainment.howstuffworks.com/golf-club.html
• Jorgensen, Theodore P., The Physics of Golf,
  American Institute of Physics Press, Woodbury,
  NY. 1994
• sportsillustrated.cnn.com/augusta/cool_stuff/physi
  cs/tiger.html