Angular Motions - Biomechanics PDF

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Angular Motions Movement about a fixed axis of rotation  Rotation about a point of contact (e.g. floor, bar…)  Rotation about the centre of mass (aerial activities)  Rotation of body segments about the joint centre Angular motion relates to rotating or spinning bodies/objects.  Measured in radians  One radian is equal to the radius of the circle  Can also be measured in degrees  1 radian = 57.3 degrees  Full circle = 6.28 radians OR 360 degrees

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Angular Distance (θ)  Scalar quantity  Sum of the angles through which an object moves  Measured in radians or degrees Angular Displacement  Vector quantity  Measures rotational movement between initial and final positions  Measured in radians Angular Velocity (ω)  Vector quantity  Measures the rate of change of angular position  Measured in rad·s-1 or ∘·s-1  Angular velocity(ω)= (∆angular displacement)/∆time  ω=∆θ/∆t Angular Accelaration (α)  Vector quantity  Rate of change of angular velocity  Unit of measurement: rad·s-2 or ∘·s-2  angular acceleration (α)= (∆angular velocity)/∆time  α=∆ω/∆t Moment of Inertia  A body’s resistance to angular motion  The angular equivalent of mass  Describes the distribution of mass about the centre of mass  It is changeable (not fixed like mass) Angular Momentum

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 Quantifies he amount of rotational motion  The product of moment of inertia and angular velocity  Vector quantity (magnitude and direction) L=I × ω kg·m^2·s^(-1)=kg·m^2 ×〖rad·s〗^(-1) Example: A performer attempting a double somersault requires more angular momentum compared to that needed when attempting a single somersault Moment of Inertia Moment of inertia is the ratio of angular momentum to angular velocity: moment of inertia(I)= (angular momentum (L))/(angular velocity (ω)) Application People in sports alter their moment of inertia in order to change the amount of rotation that occurs. By increasing/decreasing the moment of inertia sports people can alter their resistance to rotation. By increasing the moment of inertia the angular velocity is reduced. Angular momentum remains constant....