Biomechanics

• Newtons law of linear motion

  Motion in a straight or curved line, with all body parts moving the same distance at the same speed in the same direction
• Newton's First Law

  Law of Inertia
• Newton's Second Law

  law of acceleration
• Newton's Third Law

  Law of action and reaction
• Newton's First Law of inertia

  A force is required to change the state of motion. Every body will continue in its state of rest or motion in a straight line unless compelled to change by a large enough external force exerted upon it
• newtons second law of acceleration

  The magnitude (size) and direction of the force determines the magnitude and direction of the acceleration. Force = mass x acceleration. The rate of momentum of a body (or the acceleration for a body of constant mass) is proportional to the force causing it and the change that takes place in the direction in which the force acts.
• newtons third law of action/reactions


  for every action force there is an equal and opposite reaction force.
• speed equation

  distance/time
• distance

  speed x time
• Centre of Mass (COM)

  the point of balance of a body or the point of concentration of mass
• factors affecting stability

  Height of centre of mass

  Position of line of gravity

  Area of support base

  Mass of performer
• first class lever

  The fulcrum is positioned between the effort and resistance (load)
• second class lever

  the load (resistance) is between the fulcrum and the effort
• third class lever

  the effort is between the resistance (load) and the fulcrum
• Mechanical Advantage (MA)

  effort arm is longer than the resistance arm (load)
• mechanical disadvantage

  resistance arm is longer than the effort arm
• effort/ resistance arm is measured by

  distance from effort/resistance from fulcrum
• first class lever example

  Head and neck during flexion + extension and extension of elbow
• second class lever example

  plantar flexion
• third class lever example

  biceps in flexion of elbow
• Mass


  quantity of matter in the body (kg)
• distance


  path a body takes as it moves from starting position to finishing position (m)
• Speed


  body movement per unit of time with no reference to the direction (m/s)
• weight

  the gravitational force exerted on an object (N)
• weight formula

  mass (kg) x gravity(N/kg)
• Displacement


  shortest route in a straight line between the starting point and the finishing line (m)
• velocity


  rate of change of displacement. (m/s)
• Acceleration

  rate of change of velocity (m/s squared)
• Velocity formula

  displacement (m) /time (s)
• Accerleration formula

  change in velocity(m/s) / time (s)
• momentum


  the product of the mass and velocity of an object (Kgm/s)
• momentum formula

  mass (kg) x velocity (m/s)
• friction

  static = before sliding. Sliding = two. surfaces that are moving relative to one another
• friction can be affected by:

  surface characteristics, temperature of surfaces, mass of objects that are sliding
• air resistance

  opposes the motion of objects that move through the air
• air resistance is affected by:

  velocity, cross-sectional area of the moving body, shape and characteristics of moving body
• scalar quantity


  a measurement that has magnitude (size) only
• vector quantity

  a quantity that has both magnitude and direction (forces)
• Impulse formula


  force x time
• impulse (N)


  time taken for a force to. be applied to an object or body