Abstract
It is available to grasp the angular displacement of a human body for instruction on a sport performance. Provided the instantaneous angular velocity is known, the angular displacement may be obtained by the integration of it. However, although the angular velocity and the rotational axis of a rigid body can be easily derived, how should the angular velocity of a flexible body be defined? The main purpose of this paper is to define the angular velocity and the rotational axis of a whole flexible body system. A family of compact generalized formulations of rotational motion for a flexible body or multibody is derived by adopting an instantaneous rotational axis of the whole body. Here, the current angular momentum of the whole flexible system is equated with the sum of the individual angular momentum on each element over the system. As an example, simulation of a motion analysis of human body on a sport, especially throwing motion analysis of a shot put, is carried out in order to verify the derived equations in the paper
