Biomechanics

• Linear motion


  Motion where all parts of the body travel the same distance, in the same direction

  eg downhill skier
• Angular motion


  Motion where a body moves around an axis of rotation

  eg ice skater twirl
• General motion


  Combination of linear and angular motion

  eg cyclist, runner
• Classes of levers

  • Axis (fulcrum)
  • Resistance (load)
  • Force (Effort)
• Projectile


  An object propelled into the air or water by an external force
• Trajectory


  The path of a projectile
• Angular displacement


  The difference in the angle between the start and end position of the body
• Angular distance


  The exact length of an angular path

  sum of all angles as body moves from start to end position
• Acceleration


  Rate at which the velocity of a body changes with respect to time

  final velocity-initial velocoty/time
• Velocity


  Speed in a given direction

  displacement/time
• Speed


  rate at which a body moves from one point to another

  distance/time
• Distance


  Path of a body as it moves from one location to another
• Displacement


  distance between start and end point
• Theoretical optimal angle of release for distance is 45° provided height of release and landing height remain equal
• Positive acceleration means velocity is increasing
• Negative acceleration means velocity is decreasing
• Zero acceleration means no change in velocity
• The speed of release is the most important factor when maximising the distance travelled
• Static balance


  When an object is at rest and not moving
• Dynamic balance


  When an object is in motion
• Base of support


  Area bound by the outermost regions of contact between a body and support surface
• Centre of gravity


  The point around which a body’s weight is equally balanced in all directions
• In sports like High Jump and Pole Vault


  Athletes position their COG outside of their body to achieve maximum height
• Factors affecting balance and stability

  • Mass of the object
  • Size of the object's base of support
  • Height of the COG above the base of support
  • Position of the line of gravity relative to the base of support
  • positioning the COG near the edge of the base of support
• The greater the mass of an object, the greater its stability will be
• Low COG increases stability, while high COG decreases stability
• Movement is easier when the line of gravity falls outside the object’s base of support
• When receiving service in tennis, players sway from side to side keeping the centre of weight in motion across the base of support
• Force is the pulling or pushing effect of a body on another body
• Effects of force


  • 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
• Internal forces


  Action of muscles and tendons on the skeletal system
• External forces


  • Gravity
  • Friction
  • Air resistance
  • Water resistance
• Newton’s First Law of Motion: 'A body remains in its state of rest or state of motion until acted upon by a force'
• Inertia describes the amount of resistance to a change in an object's state of motion
• The greater an object's inertia, the greater the force required to initiate its movement or change its state of motion
• To move an object


  The object's inertia must be overcome
• The net external force must be greater than the inertia of the object to overcome it
• A golf ball will remain stationary on the tee until a force is applied to it
• An object moving at a constant velocity

  Will continue in a straight line unless an external force is applied
• Gravity applies a downward force on a golf ball