angular kinetics

• Inertia:

  ·      Tendency of a body to resist a change in its state of motion.

  Moment of Inertia:

  ·      Inertial property for rotating bodies= resistance to angular acceleration.

  ·      Moment of inertia = (m + r 2 )

  ·      As radius is squared= radius has most influence
• Radius of gyration:

  ·      Distance from axis of rotation to a point where the body’s mass could be concentrated without altering its rotational characteristics.

  ·      I (moment of inertia)= m (mass) x k2. (distance known as radius of gyration)
• Angular momentum: Quantity of angular motion possessed by a body.

  ·      Product of moment of inertia and angular velocity.

  ·      H= I x w

  ·      H= mk2w
• Factors affecting:

  ·      Mass (increased mass= proportional increased H).

  ·      Distribution of mass (smaller distribution= increased H- most important)

  ·      Angular velocity (increased velocity= proportional  increased H)
• Transfer of angular momentum:   

  • Pike position = large discrepancy of radius of gyration for upper/lower segments with respect to long axis of two major segments
• Conservation of angular momentum:

  ·      When gravity only acting external force= momentum is conserved.
• angular impulse= Tt = torque x time.
• ·      ˚∆H (Angular impulse)=  T(F x d) t (time).
• Angular momentum from take off depends on:

  ·      Reaction force e.g. with springboard.

  ·      Moment arm with respect to driver’s centre of gravity (d).
• angular newtons laws.

  Angular law of inertia:

  ·      A rotating body will maintain a state of constant rotational motion unless acted on by an external torque.

  Angular law of acceleration:

  ·      Net torque produces angular acceleration of a body that is:

  ·      Directly proportional to magnitude of torque.

  ·      In the same direction as the torque.

  ·      Inversely proportional to the body’s moment of inertia.

  Angular law of action-reaction:

  For every angular action there is an equal and opposite angular reaction exerted by the second body on the first.