Angular Motion

• Angular Motion

  movements of a body or part of a body in a circular path about an axis or rotation

  Results From:

  an eccentric force being applied to a body, where the force is applied outside the bodys CoM
• Torque

  another word for eccentric force (turning or rotational force )
• Axis of Rotation

  • longitudinal
  • transverse
  • frontal

  
• Angular Motion Descriptors

  • angular velocity
  • moment of inertia
  • angular momentum
• Angular Velocity

  the rate of change in angular displacement

  measures in radians per second (rad/s)

  
  

  angular velocity = angular displacement/time taken
• Moment of Inertia

  the resistance of a body to change its state of angular motion or rotation

  measured in kilograms metres squared (kgm2)

  
  

  moment of inertia = mass X distribution of mass from axis of rotation
• Factors Affecting Moment of Inertia

  • mass - the greater the mass of a body the greater the MI & vice versa, low mass decreases MI & the resistance to change state of rotation
  • distribution of mass from axis of rotation - the further the mass from the axis of rotation, the greater the MI & vice versa
• Angular Momentum

  the quantity of angular motion possessed by a body

  measured in kilogram metres squared radians per second (kgm2rad/s)

  angular momentum = moment of inertia X angular velocity
• Graph of Angular Velocity, Momentum & Angular Momentum

  • eccentric force from springboard/floor is acting on body, angular momentum & rotation around transverse axis
  • at start straight body position, MI is high & AV is low, slow rotation & dive begins with control
  • in middle tucked body position, MI is decreased & AV is increased, fast rotation due to low distribution of mass from axis of rotation
  • at end preparing for landing, MI is increase & AV is decreased, rate of spin decreases giving control of landing/entry into water due to increased distribution of mass from axis of rotation

  
• Conservation of Angular Momentum

  angular momentum is a conserved quantity which remains constant unless an external eccentric force/torque is applied
• Angular Analogue of Newtons First Law of Motion

  the angular equivalent of Newtons first law which states - a rotating body will continue to turn about its axis of rotation with constant angular momentum unless acted on by an eccentric force/external torque