Biomechanics

• Newton’s first law: inertia

  • a body will remain stationary until a large force is applied

  Newton’s second law: acceleration Force=mass x acceleration

  • if large enough force is applied the object will:
  • accelerate in the direction
  • accelerate in proportion to the amount of force allowed
• Newton’s third law: action/reaction

  • for every action there is an equal and opposite reaction

  Ground reaction force: force used to push off the ground
• Factors affecting stability:

  • height of centre of mass
  • area of the base of support
  • position of the line of gravity
  • mass of the performer
• Mechanical advantages: refers to where the effort arm is longer than the resistance arm. Mechanical advantage is highest at the second-class lever, although it does have a limited range of movement.

  Mechanical disadvantage: refers to where the resistance arm is longer than the effort arm. A third-class lever cannot apply much force to move an object.
• First class lever:

  • tricep extension

  second class lever:

  • plantar flexion of the ankle

  third class lever:

  • biceps flexion
• Vector factors:

  • mass: the quality of matter the body possesses
  • weight: measured in Newtons (N), the amount of gravity applied to mass. Calculated as mass (kg) x gravity (9.8) displacement (m) ÷ time (s)
  • speed: distance ÷ time
  • velocity: measured in metres per second, the rate of displacement
• Impulse: is the time it takes for a force to be applied to an object or body.

  Equation:

  Impulse = force X time
• Angular displacement: is the smallest change in an angle between the start and finish points of a rotation.

  Angular velocity: is the rotational speed of an object.

  Angular acceleration: is the rate of change of angular velocity.

  Equations:

  Angular velocity= angular displacement/ time take

  Angular acceleration= change in angular velocity/ time taken
• Horizontal displacement: is the shortest distance from the starting point to the finishing point.

  Factors affecting displacement:

  • angle of release (45 degree is optimum)
  • speed of release (faster the better)
  • height of release (higher the better)
• Drag: is a force which Acts in Opposition to motion.

  • surface drag: friction
  • form drag: related to streamlining

  If the object is streamlined the impact of the fluid environment is minimal
• Amount of drag is affected by:

  • velocity- greater the velocity, the greater the drag
  • area- wider the object, the greater the effect of drag
• The Bernoulli principle:

  It states that the more lift a sporting object has, the longer and further it will fly.

  explains how air molecules exert less pressure when they travel faster and more pressure when they travel slower.
• Bernoulli principle: discus

  • air travels quickly above the discus, creating low pressure
  • Air travels slowly below the discus, creating high pressure
  • pressure moves form high to low, causing the discus to lift