biomechanics

• Force


  A push or pull that alters the state of motion of a body
• Inertia


  The resistance of a body to change its state of motion, whether at rest or while moving
• Velocity


  The rate of change in displacement
• Momentum


  The quantity of motion possessed by a moving body - mass x velocity = kgm/s
• Acceleration


  The rate of change in velocity - (final velocity - initial velocity)/time = m/s/s
• Net force


  The sum of all forces acting on a body, also termed resultant force. It is the overall force acting on a body when all individual forces have been considered
• Balanced forces


  These occur when 2 or more forces acting on a body are equal in size and opposite in direction. Net force = 0, the body will remain at rest or in constant velocity
• Unbalanced forces


  These occur where 2 of more forces are unequal in size and opposite in direction. A net force will be present and the body will change its state of motion, wither accelerating or decelerating
• Weight


  The gravitational pull that earth exerts on a body - mass x acceleration due to gravity = N
• Reaction


  The equal and opposite force exerted by a body in response to the action force placed upon it
• Friction


  The force that opposes the motion of two surfaces in contact
• Air resistance


  The forced that opposes the motion through the air
• Streamlining


  The creation of smooth air flow around an aerodynamic shape to minimise air resistance
• Free body diagram


  Diagram showing all the forces acting on a body at a particular instant in time
• Centre of mass


  The point at which a body is balanced in all directions, the point from which weight appears to act
• Stability


  The ability of a body to resist motion and remain at rest
• Mechanical advantage


  Second class lever system where the effort arm is greater than the load arm. A large load can be moved with a relatively small effort
• Mechanical disadvantage


  Third class lever system where the load arm is greater than the effort arm. A large effort is required to move a relatively small load
• Linear motion


  Movement of a body in a straight or curved line, where all parts move the same direction, in the same direction over the same time
• Direct force


  A force applied through the centre off mass resulting in linear motion
• Distance


  The total length covered from start to finish
• Displacement


  The shortest straight line route from start to finish
• Speed


  The rate of change in distance - distance/time = m/s
• Deceleration


  The rate of change in velocity - m/s/s
• Angular motion


  Movement of a body or part of a body in a circular path about an axis of rotation
• Eccentric force


  A force applied outside the centre of mass, resulting in angular motion
• Torque


  A measure of the turning force applied to a body
• Principal axis of rotation

  An imaginary line that passes through the centre of mass about which a body rotates - longitudinal, transverse, frontal
• Radian


  A unity of measurement of the angle through which a body rotates
• Angular velocity


  The rate of displacement measured in radians per second
• Moment of inertia


  The resistance of a body to change its state of angular motion or rotation
• Angular momentum


  The quantity of angular motion possessed by a body
• Conservation of angular momentum

  A conserved quantity which remains constant unless an external eccentric force or torque is applied
• Angular analogue of Newton's first law of motion


  The angular equivalent of Newton's first law of motion, which states: a rotating body will continue to turn about its axis of rotation with constant angular momentum unless acted upon by an eccentric force or external torque
• Drag


  The force that opposes the direction of motion of a body through water
• Streamlining


  The creation of smooth air flow around an aerodynamic shape
• Aerofoil


  A streamlined shape with a curved upper surface and flat lower surface designed to give an additional life force to a body
• Projectile motion


  Movement of a body through the air following a curved path under the force of gravity
• Projectile


  A body that is launched into the air losing contact with the ground surface, such as a discus or a long jumper
• Resultant forces


  The sum of all the forces acting on a body or the net force acting on the projectile