Sport studies

1
Sport studies

• biomechanics

2
Some definitions

• Velocity speed in a given direction
• Acceleration rate of change of velocity
• Force a push or pull that changes the state of
  motion of an object
• Inertia resistance to action or change
• Momentum the quantity of motion that occurs

3
Newtons first law of motionLaw of inertia

• A body at rest or moving with constant velocity
  in a straight line, will continue in that state
  until a force of sufficient magnitude occurs to
  overcome its inertia
• Basically, an object will not move until you
  apply a force that is large enough to move it
• If it is moving, it will remain on that path,
  unless a force great enough is applied in a
  different direction

4
Newtons second law of motionLaw of acceleration

• This law states that the acceleration of a body
  is proportional to the force acting on it and
  that the acceleration takes place in the
  direction in which the force acts
• Basically.. the greater the applied force, the
  greater its acceleration will be
• This law also takes into account the fact that
  the accelerating effects will vary depending on
  the mass of the body which experiences the force
• Therefore.. For a greater mass, a lager amount of
  force is needed to provide the same acceleration

5
Newtons third law of motionLaw of
action/reaction

• When on object exerts a force on a second object
  there is force equal in magnitude, but opposite
  in direction exerted by the second object on the
  first
• So.. For every action there is an equal, but
  opposite reaction
• Eg. A sprinter on the blocks experiences a force
  propelling him forward. As the athlete pushes
  backwards and downwards on the blocks, the blocks
  push the athlete upwards and forwards out of the
  blocks ground reaction force

6
forces

• Internal forces produced by the muscles
• External forces gravity, air resistance etc.
• Force can
• Get objects moving
• Stop objects moving
• Change the direction of a moving object
• Change the speed of a moving object
• Balance another force to keep an object still

7
Gravity

• Gravity is a constant force
• Gravity provides a constant force on matter,
  which is commonly known as weight
• Weight is mass multiplied by gravity
• Gravity causes objects to travel towards the
  earth at a constant rate of acceleration
  (10m/sec²)

8
Centre of gravity

• The centre of gravity is defined as the point
  around which a bodys weight is equally balanced
  in al directions
• Single segmental objects have their own centre of
  gravity directly above the base of support.
• Sometimes the centre of gravity can be outside
  the body (eg.Arc)

9
Human body centre of gravity

• Standing still the centre of gravity is located
  in the abdominal cavity, about 6 inches above the
  pubis symphysis
• As your position changes so does your centre of
  gravity
• The position of the centre of gravity will
  determine whether the body is in balance
• Stability and balance will be easier if
• The mass is large
• The base is large
• The centre of gravity is low
• The centre of gravity is located over the base

10
Impulse

• Impulse is the product of the force that is
  applied to an object and the length of time the
  force is applied
• When a force is applied to an object, the product
  of the force (F) and the length of time (t) that
  the force is applied, is called the impulse of
  the force
• Impulse Ft
• Impulse is equal to force X time, measured in
  Newton seconds
• it depends on
• The time for which the force acts
• The size of the force applied

11
Momentum

• Refers to the quantity or amount of motion
• Momentum mass X velocity

12
Impact

• The size/force applied between objects during
  collision
• The greater the momentum, the greater the impact

13
Frictional force

• Acts on the interface of surfaces which are in
  contact and acts in the opposite direction of
  motion
• The co-efficient of friction indicates the ease
  of momentum i.e. the larger the co-efficient of
  friction, the harder the movement is

14
Projectiles

• Height of release
• Shotputters release the shot well above shoulder
  height, with the shot landing at ground level
• If the shotputter could release the shot from
  ground level the optimum angle of release would
  be at 45
• Angle of release
• The shape of the objects flight path is dependant
  on the angle it is released at
• If ball is thrown straight up it will go directly
  upward and pulled straight back down by gravity
• If ball is thrown at an angle above 45 it will
  have a trajectory in which height dominates over
  distance

15

• Speed of release
• If you throw with a faster arm action, it will go
  further
• Air resistance doesnt really have an affect on
  the shotput, because it is heavy

16
Net force

• All force acting upon a body or object
• Ice puck example,
• Net force is 0 when puck is resting on surface of
  ice because vertical forces acting on puck cancel
  each other out
• When the hockey stick strikes the puck, an
  additional force is introduced, causing the puck
  to accelerate during the period of time the stick
  and puck are in contact
• Once contact between the puck and stick is
  broken, there is a zero net force situation
  again. Therefore, according to Newton's 1st law
  of motion the puck will continue to travel at a
  constant velocity