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Moment of inertia and angular momentum
Published in Paul Grimshaw, Michael Cole, Adrian Burden, Neil Fowler, Instant Notes in Sport and Exercise Biomechanics, 2019
Figure C6.1 shows the moment of inertia values in some selected athletic situations during sport. It is important to reiterate that moment of inertia is specific to the axis of rotation about which the body is moving (e.g. either the centre of gravity (transverse) axis of the body as in diving or the high bar (transverse axis) in gymnastics). The greater the spread of mass from the rotation centre (axis) the greater will be the moment of inertia. In Figure C6.1 the largest moment of inertia value is determined when the body is in the position when it is rotating about the wrist (hands) and the whole body is extended (i.e. the mass is distributed as far as possible away from the axis of rotation which in this case is about the hands (an axis of rotation through the hands)). Therefore, the moment of inertia of an object or body about a particular axis depends upon the mass of the object or body and the distribution of this mass about the axis of rotation. Specifically, an equation for moment of inertia about an arbitrary axis A can be given as: Moment of inertia = mass × radius2 (kg.m2)(about an axis A)IA = m × r2
Kinetics in Angular Motion
Published in Emeric Arus, Biomechanics of Human Motion, 2017
Rotational inertia or moment of inertia (I) is a measure of how difficult it is to change the rotational velocity of an object that is rotating about an axis. The moment of inertia depends on the total mass of the object as well as the distribution of the object mass about the axis of rotation. Further, the mass from the axis is greater than the moment of inertia, so the moment of inertia is directly proportional to the object’s mass.
A preference test on shoes with varied distributions of masses
Published in Footwear Science, 2019
When the moment of inertia along the shortest axis of rotation (I1) increases (or the length of the object increases), the perceived weight increases; when the moment of inertia along the longest axis of rotation (I3) increases (or the width of the object increases), the perceived weight decreases. According to Hajnal et al. (2007), when wielding a nonvisible rod of 200–350 g with a hand or a foot, an individual can attend to and report the length of a part of the rod. When the length of the rod is increased, he or she can feel the change of the length; when the rod remains the same but I1 increases, he or she will feel that the length of the rod is increased. This happens whether the individual wields the rod either with his/her hand or with his/her foot.