Motion

• Why do coaches use biomechanics?

  -          Optimize performance

  -          Reduce injury risk

  -          Improvements for Equipment Design and Materials

  -          Develop Efficient Technique through analysis

  -          Transfer of skills from practice to the playing field

  -          Modification to equipment to increase participation in sport
• Kinematics 


  the area of biomechanics that studies the description of motion
• 3 types of movement/motion


  linear, angular, and general
• Motion: occurs when an object changes position in space and time due to the application of forces.
• Internal Force 


  Structures of the body that interact to produce movement
• External Force 


  a result of the interaction between the body and environment. These can include contact forces and non-contact forces.
• Linear Motion


  Takes place when a body moves so that all parts of the body travel the same distance, in the same direction at the same speed (no rotation)
• Curvilinear / Curved Line 


  Movement is linear, but objects move through a curved trajectory. E.g. goal shot in netball or flight path of a long-distance ski jumper.
• Distance (d) 


  refers to the path of a body as it moves from one location to another. May or may not be a straight line. Measured in metres (m) --> (how far you move)
• Displacement 


  difference between a person’s start and finish locations. Is found by measuring the length of a straight line joining a body’s initial and final positions and noting the direction this line takes.  E.g. if a marathon runner starts and finishes in the same location then her displacement after running the 42.2km race would be zero (0)
• Inertia 


  the tendency of a body to maintain it’s state of rest or uniform maintain unless acted on by an external force. It is directly related to an object’s mass --> the greater the mass, the greater the force required to move it.
• Newton's First Law 


  "Every body continues in it’s state of rest or motion in a straight line unless compelled to change that state by external forces exerted upon it”
• Speed 


  The rate at which a body moves from one location to another: -          DISTANCE ÷ TIME TAKEN = SPEED à e.g. 100m ÷ 10s = 10m/s
• Average Speed

  total distance covered divided by the elapsed time to cover that distance: Total distance ÷ Total Time = Average Speed
• Instantaneous Speed 


  speed at a given point in time:

  o   Distance ÷ time = instantaneous speed
• Velocity (v) 


  is a vector quantity that describes the speed of an object in a specific direction. It indicates how fast something is moving and in which direction.
• Velocity Equation

  DISPLACEMENT (s) (measured in m)  ÷ TIME TAKEN (seconds)  = VELOCITY (m/s)
• Mass (i) x Velocity (v) = Linear Momentum (kg m/s)
• Acceleration


  Is the rate at which the velocity of a body changes with respect to time. Directly related to mass and applied force.
• Change in velocity (final v – initial v) ÷ Time Taken = Acceleration
• positive Acceleration

  velocity is increasing
• Negative Acceleration


  velocity is decreasing
• Zero Acceleration


  no change in velocity
• Acceleration due to gravity 


  naturally occurring force resulting in downward acceleration on a body at a constant rate of – 9.8m/s
• Uniform Acceleration 


  When a body accelerates at a constant rate in both magnitude and direction
• Angular Motion 


  takes place when a body moves around an axis of rotation so that all parts of the body travel through the same angle, in the same direction, in the same time. e.g. a diver performing a somersault
• 3 Axes of rotation

  Medial Axis

  Longitudinal Axis

  Horizontal Axis
• Medial Axis 


  Navel to lower back e.g. gymnast performing cartwheel
• Longitudinal Axis

  Head to toe vertically e.g. ice skater spinning
• Horizontal Axis 


  Hip to hip e.g. diver performing forward somersault
• Axis of Rotation

  A) Medial Axis

  B) navel to lower back

  C) Longitudinal Axis

  D) head to toe verically

  E) Horizontal Axis

  F) Hip to hip

  
• General Motion


  most human motion is categorised as this type of motion. It is a combination of both linear and angular motion. E.g. running:

  There are at least 3 simultaneous rotations taking place:

  1.      Rotation of thigh @ the hip joint

  2.      Rotation of leg @ the knee joint

  3.      Rotation of foot @ the ankle joint