PE Unit 1 AOS 1: Skill Acquisition + Biomechanics

• Biomechanics


  The study of the mechanical principles that govern human movement.
• Benefits of Biomechanics


  - optimisation of sports performance

  - prevention and reduction of injury

  - improved design and development of equipment
• Qualitative movement analysis


  The systematic observation and judgement of the quality of human movement for the purpose of providing appropriate intervention to improve performance.
• Quantitative movement analysis


  The systematic observation of motion based on data collected during the performance.
• Types of equipment

  - Accelerometers

  - Light gates

  - Force plates

  - Video analysis
• Define Kinetics


  The study of the forces that create motion.
• Define Force


  Any pushing or pulling action resulting from an objects interaction with another object that alters the state of motion of the object.

  
  

  Force (Newtons) = Mass x Acceleration
• Forces influencing sports performance


  - Friction

  - Air resistance

  - Gravitational force

  - Weight
• Friction


  A force that opposes the motion of an object, occurring when two surfaces come into contact with each other.
• Types of friction

  Sliding friction: resistance created between the surface of any two objects sliding against one another.

  Rolling friction: force between the surface of a rolling body against a surface that resists its motion.
• Factors affecting friction

  - Nature of the surface of the object

  - Nature of the surface that the object is move against.

  - Size/radius of the objects surface area.

  - Weight (weight is directly proportional to friction)
• Drag force


  A force that opposes the motion of an object through a fluid (air or water).
• Manipulating Drag force


  Athletes can reduce the effects of air/water resistance by:

  - Shaving body hair,

  - Wearing swim caps/body suits

  - Adopting streamlined positions.
• Gravity


  A constant force that pulls an object down towards earth.
• Weight


  The force that is exerted on the body by the force of gravity:

  Weight (N) = Mass x Gravity
• Inertia


  The tendency for a body to resist a change in its state of motion, whether at rest or moving with a constant velocity.
• Relationship: Mass x Inertia

  The inertia of an object is directly proportional to its mass.

  
  

  The greater the mass of an object, the greater its inertia, therefore the greater the amount of force is needed to change its state of motion.
• Define Momentum


  Describes the quantity of motion that a particular body of mass has:

  
  

  Momentum (ks/m/s) = mass x velocity.
• Momentum of objects


  - A stationary object with 0 velocity will have 0 momentum.

  - The greater the momentum of an object, the more difficult to stop or slow down its motion, causing it to travel farther.
• Law of the Conservation of Momentum


  Principle states that the sum of momentum present prior to a collision is equal to the sum of momentum after a collision occurs.
• Force Summation


  The correct timing and sequencing of body segments and muscles through a range of motion.
• Simultaneous force summation


  Involves an explosive action using all body parts that occurs at the same time to produce force.

  E.g. jumping for a block in volleyball.
• Sequential force summation


  The activation of body parts in a sequence to generate great force.

  E.g. throw in discus
• Principles of sequential force summation


  Number - utilises as many body parts as possible

  
  

  Order - activation of larger, stronger (slower) muscles/body parts first.

  
  

  Stability - Each body part successively stabilises for maximal acceleration, so the next part accelerates around a stable base, so momentum can be transferred successfully.

  
  

  Timing - each body part accelerates sequentially, transferring momentum from one body part to the next when at maximum velocity.
• Linear Motion

  The motion of a body/object that travels along a straight or curved path, where all parts of the body move in the same direction at the same speed.

  
  

  e.g. a swimmer gliding off the wall
• Kinematic concepts of Linear Motion

  - distance + displacement

  - speed + velocity

  - acceleration
• Define Speed


  The rate of motion.

  
  

  Speed (m/s) = distance (m) / time (s)
• Define Velocity


  Velocity: A measure of the change in displacement over a period of time.

  *Velocity is expressed in both size and direction (30 m/s north).

  
  

  Velocity = displacement / time
• Acceleration (linear motion)


  The change in velocity over a given period of time.

  
  

  Acceleration (m/s/s) = velocity (m/s) / time(s)

  
  

  Acceleration = Force / Mass
• Newtons First Law of Motion: Law of Inertia


  An object whether at rest or in motion will continue in that state of motion unless acted on by an external force great enough to change its state of motion or rest.

  
  

  e.g. a soccer ball won't move from its position unless a force acts upon it, such as being kicked.
• Newtons Second Law of Motion: Acceleration


  The acceleration of an object is directly proportional to the amount of force applied and takes place in the direction that force is applied.

  
  

  F = M x A

  
  

  e.g. a tennis ball will accelerate faster than a netball when thrown with the same force since it is lighter.
• Newtons Third Law of Motion: Action-Reaction


  For every action there is an equal and opposite reaction.

  
  

  e.g. a swimmer applies pushes off a diving platform, which applies an equal and opposite force against the swimmer, causing them to launch into the water.
• Define Angular motion (rotary motion)


  The motion of a body or object that turns about a fixed point or central axis.

  
  

  e.g. a gymnast rotating around the high bars. (axis of rotation) is an example of angular motion.
• Distance (angular)


  Measures the amount of degrees an object passes through from start to finish.
• Angular displacement.


  Measures the amount of degrees the object moves from the starting point.
• Angular velocity


  Measure of how quickly an object has moved from its starting point and in what direction it has moved.
• Angular acceleration


  Measure of the rate of change of angular motion.
• Impulse


  A change in the momentum of a body/object.

  
  

  A measure of force applied over time.

  
  

  Impulse = force x time.
• Manipulating Impulse - Increasing Momentum

  - The greater the impulse, the greater the momentum generated.

  
  

  - The greater the amount of time maximal forces can be applied, the greater the impulse and resultant momentum.

  
  

  e.g. a baseball batter performing a backswing when hitting is an example of increasing impulse, since the amount of time force is applied is increased, resulting in increased momentum.
• Manipulating Impulse - Force Reception

  - A body/object that is no longer in contact with a platform applying force cannot change its impulse.

  
  

  - Force and time are inversely proportional as the net impulse cannot be changed.

  
  

  - Increasing the time the force is applied/received will decrease the overall force/prevent injury.

  
  

  e.g. a high jump mat increases the time force is absorbed, reducing the force of the impact.