Biomechanics Lecture 6 (Angular kinetics)

Moment of inertia

Inertial property for rotating bodies, represents resistance to angular acceleration, based on both mass and the distance the radius of gyration

Moment of Inertia equation

I = m x k^2

radius of gyration

distance from the axis of rotation to a point, used as the mass distribution for calculating moment of inertia, distribution of forces above the axis of rotation

Angular Momentum

Quantity of angular MOTION possessed by a body, measured as the product of moment of inertia x angular velocity

Angular momentum equation

H = I x w OR H = Mk^2w

only difference with angular momentum is that you are accounting for the

radius of gyration

principle of conservation of angular momentum

the total angular momentum of a given system remains constant in the absence of external torques (H1 = H2)

what produces change in angular momentum?

angular impulse (Tt)

angular impulse (Tt) is

the product of torque and the time interval over which the torque acts

torque is the angular equivalent of force so...

force x time = impulse

Torque x time = angular impulse

Angular law of inertia

a rotating body will maintain a state of rest or constant rotational motion unless acted on by an external torque that changes the state

Angular law of acceleration

a net torque causes angular acceleration of a body that is: of a magnitude proportional to the torque, in the direction of the torque, inversely proportional to the body's moment of inertia

angular acceleration equation

T = Ia or mk^2